Fatigue Countermeasures in Aviation - Aerospace Medical Association

POSITION PAPER 

Fatigue Countermeasures in Aviation 

John A. Caldwell , Melissa M. Mallis , J. Lynn Caldwell , 

Michel A. Paul , James C. Miller , and David F. Neri 

for the Aerospace Medical Association Fatigue 

Countermeasures Subcommittee of the Aerospace 

Human Factors Committee 

C ALDWELL JA, M ALLIS MM, C ALDWELL JL, P AUL MA, M ILLER JC, 

N ERI DF, A EROSPACE M EDICAL A SSOCIATION A EROSPACE F ATIGUE C OUN- 

TERMEASURES S UBCOMMITTEE OF THE H UMAN F ACTORS C OMMITTEE . Fatigue 

countermeasures in aviation. Aviat Space Environ Med 2009; 

80:29 – 59. 

Pilot fatigue is a significant problem in modern aviation operations, 

largely because of the unpredictable work hours, long duty periods, circadian 

disruptions, and insufficient sleep that are commonplace in both 

civilian and military flight operations. The full impact of fatigue is often 

underappreciated, but many of its deleterious effects have long been 

known. Compared to people who are well-rested, people who are sleep 

deprived think and move more slowly, make more mistakes, and have 

memory difficulties. These negative effects may and do lead to aviation 

errors and accidents. In the 1930s, flight time limitations, suggested layover 

durations, and aircrew sleep recommendations were developed in 

an attempt to mitigate aircrew fatigue. Unfortunately, there have been 

few changes to aircrew scheduling provisions and flight time limitations 

since the time they were first introduced, despite evidence that updates 

are needed. Although the scientific understanding of fatigue, sleep, shift 

work, and circadian physiology has advanced significantly over the past 

several decades, current regulations and industry practices have in large 

part failed to adequately incorporate the new knowledge. Thus, the 

problem of pilot fatigue has steadily increased along with fatigue-related 

concerns over air safety. Accident statistics, reports from pilots themselves, 

and operational flight studies all show that fatigue is a growing 

concern within aviation operations. This position paper reviews the relevant 

scientific literature, summarizes applicable U.S. civilian and military 

flight regulations, evaluates various in-flight and pre-/postflight 

fatigue countermeasures, and describes emerging technologies for detecting 

and countering fatigue. Following the discussion of each major 

issue, position statements address ways to deal with fatigue in specific 

contexts with the goal of using current scientific knowledge to update 

policy and provide tools and techniques for improving air safety. 

Keywords: alertness , sleep , hypnotics , stimulants , flight time regulations , 

duty time regulations , sustained operations . 

FATIGUE COUNTERMEASURES IN AVIATION: 

OUTLINE OF CONTENTS 

I. Description of the Problem 

II. Current Regulations, Practices, and an Alternative Approach 

a. Crew Rest Guidelines 

b. Flight and DutyTime Guidelines 

c. Fatigue Risk Management System (FRMS): An Alternative 

Regulatory Approach 

d. Ultra-Long-Range Flights: A Nontraditional Approach 

Position Statement on Crew Rest, Flight, and Duty Time Regulations 

III. 

In-Flight Countermeasures and Strategies 

a. Cockpit Napping 

b. Activity Breaks 

c. Bunk Sleep 

d. In-Flight Rostering 

e. Cockpit Lighting 

Position Statement on the Use of In-Flight Countermeasures 

IV. Pre-/Postflight Countermeasures and Strategies 

a. Hypnotics 

Position Statement on the Use of Hypnotics 

b. Improving Sleep and Alertness 

i. Healthy Sleep Practices 

ii. Napping 

iii. Circadian Adjustment 

iv. Exercise 

v. Nutrition 

Position Statement on Improving Sleep and Alertness 

c. Non-FDA-Regulated Substances 

Position Statement on Non-FDA-Regulated Substances 

V. New Technologies 

a. On-Line, Real-Time Assessment 

b. Off-Line Fatigue Prediction Algorithms 

Position Statement on New Technologies 

VI. Military Aviation 

a. 

b. 

Relevant Regulations and Policies 

Crew Rest and Duty Limitations 

Stimulants/Wake Promoters 

c. 

Position Statement on the Use of Stimulants to Sustain Flight 

Performance 

d. Sleep-Inducing Agents 

Position Statement on the Military Use of Sleep-Inducing Agents 

e. Nonpharmacological Countermeasures and Strategies 

VII. Conclusions and Recommendations 

I. DESCRIPTION OF THE PROBLEM 

Pilot fatigue is a significant problem in modern aviation 

operations, largely because of the unpredictable 

work hours, long duty periods, circadian disruptions, 

This Position Paper was adopted by the Aerospace Medical Association. 

It was prepared by a special subcommittee of the Aerospace Human 

Factors Committee chaired by Dr. David Neri and consisting of 

the authors. The paper is intended to review the relevant literature, 

describe fatigue-related issues and challenges, summarize applicable 

regulations, and present the Association’s position with respect to fatigue 

countermeasures. 

This manuscript was received and accepted for publication in September 

2008 . 

Address reprint requests to: J. Lynn Caldwell, Ph.D., Air Force Research 

Laboratory, Human Effectiveness Directorate, Wright- Patterson 

AFB, OH 45433; lynn.caldwell@wpafb.af.mil 

Reprint & Copyright © by the Aerospace Medical Association, Alexandria, 

VA. 

DOI: 10.3357/ASEM.2435.2009 

Aviation, Space, and Environmental Medicine x Vol. 80, No. 1 x January 2009 29

FATIGUE COUNTERMEASURES — CALDWELL ET AL. 

and insufficient sleep that are commonplace in both civilian 

and military flight operations ( 147 , 186 ). The full 

impact of fatigue is often underappreciated, but many 

of its deleterious effects have long been known. Lindberg 

recognized the detrimental consequences of long duty 

hours (and long periods of wakefulness) on flight performance 

back in the 1920s and scientists began to appreciate 

the negative impact of rapid time zone transitions 

in the early 1930s ( 134 ). Compared to people who 

are well-rested, people who are sleep-deprived think 

and move more slowly, make more mistakes, and have 

memory difficulties. These negative effects may and do 

lead to aviation errors and accidents. In the long term, 

the irregular schedules worked by many aircrews during 

a career may lead, as they do for shift workers, to 

higher incidences of stomach problems (especially heartburn 

and indigestion), menstrual irregularities, colds, 

flu, weight gain, and cardiovascular problems. 

In the 1930s, flight time limitations, suggested layover 

durations, and aircrew sleep recommendations were developed 

in an attempt to mitigate aircrew fatigue. Unfortunately, 

there have been few changes to aircrew 

scheduling provisions and flight time limitations since 

the time they were first introduced. To add further complexity, 

scheduling and flight time regulations vary 

among different countries. 

Although scientific understanding of fatigue, sleep, 

shift work, and circadian physiology has advanced significantly 

over the past several decades, current regulations 

and industry practices have in large part failed to 

adequately incorporate the new knowledge ( 67 ). Thus, 

the problem of pilot fatigue has steadily increased along 

with fatigue-related concerns over air safety. Accident 

statistics, reports from pilots themselves, and operational 

flight studies all show that fatigue is a growing 

concern within aviation operations. 

Long-haul pilots frequently attribute their fatigue to 

sleep deprivation and circadian disturbances associated 

with time zone transitions. Short-haul (domestic) pilots 

most frequently blame their fatigue on sleep deprivation 

and high workload ( 28 ). Both long- and short-haul 

pilots commonly associate their fatigue with night 

flights, jet lag, early wakeups, time pressure, multiple 

flight legs, and consecutive duty periods without sufficient 

recovery breaks. Corporate/executive pilots experience 

fatigue-related problems similar to those reported 

by their commercial counterparts. However, again, they 

most frequently cite scheduling issues (multi-segment 

flights, night flights, late arrivals, and early awakenings) 

as the most noteworthy contributors ( 179 ). Weather, turbulence, 

and sleep deprivation, in combination with 

consecutive and lengthy duty days, time zone transitions, 

and insufficient rest periods, are blamed as well. 

Despite the many differences between civilian and military 

aviation operations, surveys of military pilots generally 

support the findings obtained from the commercial 

sector. U.S. Army helicopter pilots and crews 

frequently blame inadequate sleep and/or insufficient 

sleep quality for impaired on-the-job alertness, and like 

their commercial counterparts, they indicate that fatigue 

in general is a significant problem ( 51 ). U.S. Air Force pilots 

report the same problems ( 130 ). Noteworthy fatigue 

factors include scheduling issues (frequently changing 

work/rest periods, operating at night, etc.) and uncomfortable 

sleep conditions (leading to sleep deprivation). 

U.S. Navy fighter pilots deployed in Operation Southern 

Watch in 1992 commonly complained that sleep restriction 

aboard aircraft carriers led to somatic complaints, 

alertness difficulties, and general performance 

degradations ( 18 ). U.S. Air Force F-15 pilots in Operation 

Desert Storm indicated that around-the-clock task 

demands, minimal rest periods, consecutive duty days, 

circadian disruptions, and sleep deprivation were commonplace 

( 58 ), as did F-16 pilots ( 189 , 190 ). U.S. Air Force 

C-141 pilots in Operation Desert Storm likewise complained 

that insufficient sleep and lengthy flight times 

were primarily responsible for increased fatigue ( 147 ). 

Duty times and aircrew fatigue will continue to be a 

challenge in both scheduled passenger airlines (major, 

national, commuter) and cargo operations, especially 

with the advent of ultra-long-range (ULR) aircraft (i.e., 

. 16-h block-to-block). Both Boeing and Airbus are currently 

manufacturing ULR aircraft. These aircraft have 

resulted in operations with longer duty periods than those 

encountered in current domestic and international 

flights. They will also increase the demands for crews to 

work nonstandard and nighttime duty schedules. Thus, 

an important question for ULR operations is whether 

the strains imposed by the extension of flight duty hours 

beyond the limits commonly flown will effectively be 

mitigated by the standard fatigue countermeasures, 

which in part have been responsible for the acceptable 

safety record of existing flight operations. Without 

proper management, ULR operations may exacerbate 

the fatigue levels that have already been shown to impair 

safety, alertness, and performance in existing flight 

operations ( 143 ). 

Clearly, fatigue is not a one-dimensional phenomenon, 

but rather the product of several factors related 

to physiological sleep needs and internal biological 

rhythms. In spite of its complex nature, the operational 

causes of fatigue are strikingly consistent across diverse 

types of aviation operations. The consequences of aircrew 

fatigue are consistent as well. 

From a physiological perspective, both simulator and 

in-flight studies have documented that fatigue impairs 

central nervous system functioning. Cabon and colleagues 

( 37 ) demonstrated that long-haul pilots were 

particularly susceptible to vigilance lapses during low 

workload periods, and that such lapses could simultaneously 

appear in both crewmembers flying the aircraft 

at the same time (an obvious safety concern). In one of 

the crews evaluated, both the pilot and the copilot evidenced 

periods of increased slow-wave electroencephalography 

(EEG) activity (indicative of sleepiness) by the 

4th and 5th hour of a lengthy flight. Wright and McGown 

( 232 ) found that pilot microsleeps occurred most frequently 

during the cruise portion of long-haul operations 

(in the middle-to-late segments of the flight) and 

that microsleeps were more than nine times as likely 

30 Aviation, Space, and Environmental Medicine x Vol. 80, No. 1 x January 2009


during nighttime flights compared to daytime flights. 

Most of these lapses go unnoticed by the affected crewmembers. 

Samel and colleagues ( 187 ) essentially confirmed 

the EEG results from Cabon et al. ( 37 ) and Wright and 

McGown ( 232 ) by showing that, in general, spontaneous 

microsleeps increased with increasing flight duration. 

Also, nighttime flights were again found to be more 

problematic than daytime flights. Rosekind et al. ( 177 ) 

documented the presence of physiological micro-events 

(slow brain activity and eye movements) even during 

the period from top-of-descent to landing. In one group, 

87% of the pilots experienced at least one microsleep 

greater than 5 s in duration, and on average, the pilots 

experienced six microsleeps during the last 90 min of 

the flight. In addition to microsleeps and lapses, many 

pilots admit to having fallen asleep in the cockpit. Of the 

1424 flightcrew members responding to a NASA survey 

of fatigue factors in regional airline operations, 80% acknowledged 

having “ nodded off ” during a flight at 

some time ( 55 ). For corporate/executive airline operations, 

71% of 1488 flightcrew survey respondents reported 

having nodded off during flight ( 175 ). 

From a safety perspective, improperly managed fatigue 

poses a significant risk to crew, passengers, and 

aircraft. A National Transportation Safety Board (NTSB) 

study of major accidents in domestic air carriers from 

1978 through 1990 in part concluded that “ … Crews 

comprising captains and first officers whose time since 

awakening was above the median for their crew position 

made more errors overall, and significantly more procedural 

and tactical decision errors ” ( 139 , p. 75). Kirsch 

( 103 ) estimated that fatigue may be involved in 4 – 7% of 

civil aviation mishaps, data from the U.S. Army Safety 

Center suggest fatigue is involved in 4% of Army accidents 

( 48 ), and statistics from the Air Force Safety Center 

blame fatigue, at least in part, for 7.8% of U.S. Air Force 

Class A mishaps ( 124 ). Furthermore between 1974 and 

1992, 25% of the Air Force’s night tactical fighter Class A 

accidents were attributed to fatigue and from 1977 to 

1990, 12.2% of the U.S. Navy’s total Class A mishaps 

were thought to be the result of aircrew fatigue ( 166 ). * 

Fatigue in aviation is a risk factor for occupational 

safety, performance effectiveness, and personal wellbeing. 

The multiple flight legs, long duty hours, limited 

time off, early report times, less-than-optimal sleeping 

conditions, rotating and nonstandard work shifts, and 

* Although differences exist between civil and military operations, it 

is clear similar factors and conditions lead to fatigue in both civilian 

and military aviation environments and fatigue mitigation strategies 

for both contexts should be scientifically based. Understandably, however, 

different regulations and operational considerations have resulted 

in fatigue countermeasure approaches that differ in important ways. 

For example, a variety of pharmacological countermeasures have been 

approved for use in certain circumstances by U.S. military aviators but 

not by civilian aviators. The current prohibition regarding use of pharmacological 

countermeasures by civilian pilots can be attributed to 

safety concerns and issues of adequate policies for oversight. The military 

services have addressed these issues through targeted research, 

explicit policies on medical oversight, and recognition of the sometimes 

overriding importance of operational considerations (e.g., 

NAVMED P-6410). The use of pharmacological countermeasures to 

fatigue in civilian (but not military) pilots is addressed in this paper. 

jet lag pose significant challenges for the basic biological 

capabilities of pilots and crews. Humans simply were 

not equipped (or did not evolve) to operate effectively 

on the pressured 24/7 schedules that often define today’s 

flight operations, whether these consist of shorthaul 

commercial flights, long-range transoceanic operations, 

or around-the-clock military missions. Because of 

this, well-planned, science-based, fatigue management 

strategies are crucial for managing sleep loss/sleep debt, 

sustained periods of wakefulness, and circadian factors 

that are primary contributors to fatigue-related flight 

mishaps ( 178 ). These strategies should begin with regulatory 

considerations, but should include in-flight countermeasures 

as well as both pre- and postflight interventions. 

The risks and benefits of each technique should be 

carefully considered and balanced. 

In the following sections, this position paper will summarize 

relevant U.S. civilian and military flight regulations, 

evaluate various in-flight and pre-/postflight fatigue 

countermeasures, and describe emerging technologies for 

detecting and countering fatigue. † Following each major 

section, position statements and recommendations will be 

provided for addressing fatigue in that specific context. 

II. CURRENT REGULATIONS, PRACTICES, AND 

AN ALTERNATIVE APPROACH 

a. Crew Rest Guidelines 

The Federal Aviation Administration (FAA) regulates 

crew rest for commercial aviation ( 1 ) in documents previously 

referred to as Federal Aviation Regulations 

(FARs) and renamed the Code of Federal Regulations 

(CFRs). Crew rest, as defined by the CFRs, is any time 

that a crewmember is free from all duties and responsibilities, 

including flying and administrative work. The 

FAA places strict limitations on minimum crew rest periods. 

The minimum mandatory rest period for both 

nonaugmented and augmented flightcrews is 10 h prior 

to a duty period. (An augmented flightcrew is composed 

of more than the minimum number required to operate 

the aircraft.) Nonaugmented crews are also required to 

have a minimum 10-h rest period after the duty period 

ends. It is important to note that this 10-h rest period includes 

local travel time to and from a place of rest (but 

not the time required to preposition a crew). Including 

travel time as part of the mandatory rest time between 

flights reduces the time that flightcrew have available 

for uninterrupted sleep periods. Therefore, flightcrews 

often fail to obtain 8 h of uninterrupted sleep. For example, 

if the crew were to land at the destination airport 

and the hotel where they planned to obtain their crew 

rest was a 1-h drive away, the travel between the airport 

and hotel (in both directions) would total 2 h and be 

† U. S. civilian and military flight regulations were utilized due to 

space limitations and because of ready access compared to the corresponding 

sets of international regulations. While a full discussion in 

the context of the many international regulations is outside the scope 

of this paper, the proposed countermeasure approaches have broad 

applicability given their basis in human physiology. 



considered part of their rest time. Therefore, they would 

have 8 h maximum in the hotel to obtain recovery sleep, 

eat, and attend to personal needs. It is highly unlikely 

the crew would have the opportunity to obtain a minimum 

8- to 8.25-h sleep period, the average sleep need 

for an adult ( 222 ). However, for augmented crews, the 

rest period after duty is 12 h and is extended to 18 h for 

multiple time zone flights. While the extended time period 

is an improvement, it should be noted that none of 

the rest period guidelines account for the timing of sleep 

with respect to circadian phase, despite the fact sleep 

propensity varies significantly with time of day, making 

sleep obtained during the subjective daytime shorter, of 

poorer quality, and less restorative than nighttime sleep 

( 6 ). Instead, rest period durations are constant and independent 

of time of day. 

b. Flight and Duty Time Guidelines 

In addition to specifying crew rest times, the FAA regulates 

crew flight and duty time for commercial aviation 

( 1 ). Flight time duty limitations for the major airlines are 

covered in CFRs Part 121 and in Part 135 for commuter 

airlines ( 2 , 3 ). 

Flight time is the time between “block-out” and 

“ block-in ”. Flight time begins when the aircraft moves 

from its parked position and ends when the plane is 

parked at its destination. Although flight time and the 

workload endured throughout the flight are important, 

total duty time should be considered also when determining 

an individual’s level of alertness. Flight time is a 

subset of duty time. Duty time is longer and includes the 

time period between when pilots report for a flight and 

when they are released after a flight. Therefore, it includes 

any administrative work required by the airline. 

Maximum allowable flight time and duty time differ for 

nonaugmented and augmented crews (flight time: 10 h 

vs. 12 h and duty time: 14 h vs. 16 h). However, the augmented 

crews are limited to 8 h on the flight deck and 

are provided rest facilities for in-flight rest opportunities. 

Although maximum duty time is 2 h longer for augmented 

crews than nonaugmented crews, maximum 

flight time additive over 1 wk, 1 mo, and 1 yr are the 

same. These limits are summarized in Table I . 

An examination of crew duty and rest guidance for 

commercial versus military aviation operations reveals 

fewer similarities than differences. The primary similarity 

is the requirement for the attainment of 8 h of 

sleep, but this is far from a hard-and-fast rule. There 

are usually detailed guidelines for the manner in which 

shorter sleep durations will be handled in civil flight 

operations (e.g., by requiring a shorter subsequent duty 

period or a longer recovery period). In most cases, 

single-pilot operations are more restrictive than dualpilot 

or augmented crew operations. Especially with 

regard to long-haul flights, careful consideration must 

be given to crew duty time, onboard rest scheduling, 

layover sleep opportunities (e.g., duration and recommended 

timing), and recovery sleep after returning to 

domicile. 

TABLE I. CFRS FOR MINIMUM REST PERIODS AND MAXIMUM 

FLIGHT AND DUTY PERIODS FOR BOTH NONAUGMENTED AND 

AUGMENTED CREWS. 

Non-Augmented 

Crew (Single- or 

Two-Pilot Crew) 

Augmented Crew 

Minimum preduty 

10 h 10 h 

rest period 

Minimum postduty 

rest period 

10 h 12 h 

18 h for multiple time 

zones 

Maximum flight time 10 h 12 h 

Maximum duty time 14 h 16 h 

Maximum duty time; 

30 h 30 h 

1 wk 


100 h 100 h 

1 mo 


1 yr 

1400 h 1400 h 

c. Fatigue Risk Management System (FRMS): An 

Alternative Regulatory Approach 

Each individual type of aviation operation offers its 

own complexity, whether it be working extended duty 

days, crossing multiple time zones, sleeping at adverse 

circadian times, or performing during a circadian nadir. 

These are just a few examples of the physiologically 

relevant factors that are unique to every schedule. 

They are also affected by specific organizational needs 

and airport operating requirements. The combination 

of these factors requires a new approach that addresses 

operations on an individual case basis and also allows 

for operational flexibility. One option for approaching 

this is by addressing both physiological and operational 

factors as part of a Fatigue Risk Management 

System (FRMS). A multicomponent FRMS program, 

with a scientific foundation, helps ensure that performance 

and safety levels are not compromised by offering 

an interactive way to safely schedule and conduct 

flight operations on a case-by-case basis. Fatigue risk 

management systems offer an alternative approach to 

traditional prescriptive duty and flight time limitations 

and rest time regulations currently enforced by the 

FAA. 

An FRMS is an evidence-based system for the measurement, 

mitigation, and management of fatigue 

risk. It includes a combination of processes and procedures 

that are employed within an existing Safety 

Management System ( 195 ). It is a nonprescriptive 

way to monitor fatigue risk associated with aviation 

operations. 

Multiple groups worldwide are recommending some 

minimum requirements for an effective FRMS. Two examples 

of recommendations are provided below. 

The U.S.-based Flight Safety Foundation has suggested the following 

minimum activities as part of an effective FRMS ( 140 ): 

• Develop a fatigue risk management policy; 

• Formalize education/awareness training programs; 

• Create a crew fatigue-reporting mechanism with associated 

feedback, procedures, and measures for monitoring fatigue 

levels; 



• Develop procedures for reporting, investigating, and recording 

incidents in which fatigue was a factor; 

• Implement processes and procedures for evaluating information 

on fatigue levels and fatigue-related incidents, implementing 

interventions, and evaluating their effects. 

The Civil Aviation Safety Authority in Australia has defined impact 

areas that an FRMS must consider ( 13 ): 

• Sleep opportunity provided by schedules; 

• Sleep obtained by personnel to indicate fitness for duty; 

• Hours of wakefulness; 

• Circadian factors; 

• Sleep disorders; 

• Operational demographics. 

Other organizations are already testing the effectiveness 

of these approaches. One of the more commonly 

known efforts is easyJet’s implementation of an FRMS 

as part of their Systems Integrated Risk Assessment 

(SIRA). Preliminary results have demonstrated its effectiveness 

at reducing fatigue ( 200 ). Within the U.S., 

the Flight Safety Foundation (FSF) has suggested that 

an FRMS approach be used for ultra-long-range operations 

( 83 ). Their specific recommendations are described 

in more detail in Section d , below. FRMS programs 

are not only being explor ed in flightcrew 

operations but are being used by Transport Canada 

with Canadian aircraft maintenance engineers ( 26 ). The 

International Civil Aviation Organization (ICAO) is in 

the process of compiling a report with the recommended 

components of a FRMS. The FAA is also exploring 

ways to implement effective FRMS based programs 

in operations where fatigue has been identified 

as an inherent risk. 

d. Ultra-Long-Range Flights: A Nontraditional Approach 

Ultra-long-range (ULR) aircraft will extend the longest 

flight duty days from 14 – 16 h to 201 h. Current 

CFRs do not address this 4- to 6-h increase in flight 

duration. Consequently, there are no crew rest, flight 

time, or duty time regulations specific to ULR 

operations. 

In anticipation of the physiological challenges associated 

with proposed ULR flights, the Flight Safety 

Foundation, Airbus, and Boeing conducted four ULR 

Crew Alertness workshops that involved both scientific 

experts and aviation operational groups from 

throughout the world. These workshops were interactive, 

allowing for focused discussions of the operational 

and technological issues associated with maintaining 

maximal alertness levels during ULR operations 

( 83 ). However, the workshops not only identified the 

issues, but, with the guidance of the Steering Committee, 

developed common methods and approaches to 

reduce errors, incidents, and accidents involving fatigue. 

The recommendations were largely based on an 

FRMS program and included three main components: 

1) development of a fatigue risk management policy; 

2) formation of a Fatigue Management Steering Committee; 

and 3) implementation of education and training 

programs. Other important recommendations from 

the workshop subgroup meetings included the 

following: 

• 

• 

Mandatory in-flight rest periods (not optional for flightcrew); 

Identification of departure windows that consider delays (not 

exceeding a specified duration) and approaches to handle such 

disruptions; 

Informing flightcrew 36 to 48 h prior to departure of scheduled 

on-board bunk sleep periods; 

Recurring validation of schedules using both objective and 

subjective measures to inform management of necessary schedule 

changes. 

• 

• 

The FAA is currently using a case-by-case approach 

to approve ULR city pairs. They are approving these 

operations by issuing a nonstandard operations specification 

paragraph, (OpSpec A332) “ Ultra Long Range 

(ULR) Flag Operations in Excess of 16 Hours Blockto-Block 

Time ” to air carriers intending to conduct 

ultra-long-range operations. This paragraph contains 

requirements designed to “ optimize opportunities for 

flightcrew members to obtain adequate rest to safely 

perform their operational duties during all phases of 

this ULR trip sequence. ” OpSpec A332 has already 

been issued to one air carrier. 

As detailed in OpSpec A332, carriers proposing a ULR 

city pair are requested to present a route-specific plan to 

the FAA. The FAA reviews the routes, from both a scientific 

and operational perspective, and carefully considers 

duty times, flight times, and rest periods to assess the 

opportunities available for rest and recovery periods in 

preparation for, during, and after scheduled ULR flights. 

The carrier is also requested to provide details of the onboard 

rest scheme, plans to assure preduty minimum 

rest periods and a method for addressing delays and 

cancellations. After a careful review process, the FAA determines 

the safety of the proposed city-pair plan and 

subsequently authorizes the carrier to fly the route. Since 

issuing the original OpSpec A332, the FAA also considers 

predicted crew performance levels using the SAFTE 

model (101), a scientifically based modeling approach, 

in its evaluation of the proposed ULR operation. It can 

be an iterative process and require multiple changes in 

the proposed plan before approval is given. Other requirements 

of OpSpec A332 include both subjective and 

objective data collection during the ULR route within 

180 d of authorization for carriers to validate the effectiveness 

of the fatigue mitigation strategies included in 

OpSpec A332. The FAA requires that all ULR assigned 

crewmembers receive education and city-pair specific 

route guides that include suggested practices for maximizing 

total sleep times during ULR operations. 

Position Statement on Crew Rest, Flight, and Duty 

Time Regulations 

The prescriptive rule-making approach commonly 

used by regulatory agencies to regulate crew rest and 

flight and duty times is not derived from the foundational 

scientific research addressing the interaction of 

sleep and circadian processes and their effects on performance. 

The risks associated with nonscience-based regulatory 

approaches may have been unknown in the 

1930s when flight and duty time limits were first addressed. 

At the time, research documenting the performance 

and alertness decrements associated with sleep 



loss and circadian disruption was limited and it seemed 

sufficient to ensure safety via agreements between 

flightcrew and management. However, with the demands 

of 24/7 aviation operations, it has become increasingly 

apparent that such prescriptive approaches 

do not address inherent sleep and circadian challenges 

nor do they provide operational flexibility. 

The current FAA prescriptive regulations address 

duty time equally across all hours of the day (e.g., 8 h of 

nighttime flight duty is implicitly considered to be no 

more fatiguing than 8 h of daytime flight duty). However, 

a scientifically informed regulation would consider 

circadian placement or time of day when establishing 

work duty limits. It would also consider circadian variables 

when identifying the placement of opportunities 

for rest and sleep. 

One example that clearly shows that regulatory limitations 

are arbitrarily chosen and are not informed by 

the scientific research is the regulation specifying maximum 

yearly flight times. The maximum flight time/year 

is 1400 h in the United States but is 900 h in Australia 

( 12 ). If the establishment of yearly flight time limits considered 

human physiology and had a foundation in relevant 

sleep and circadian science, it would be expected 

that these limits would be similar among countries. 

However, this is not the case. Based on this 500 h difference, 

U.S.-based pilots are authorized to fly up to 64% 

more hours than Australia-based pilots. 

Addressing fatigue as part of a scientifically based, 

comprehensive safety management system can help to 

minimize the risk associated with current and future 

aviation operations. An FRMS offers a way to more 

safely conduct flights beyond existing regulatory limits 

and should be considered an acceptable alternative to 

prescriptive flight and duty time and rest period 

regulations. 

III. IN-FLIGHT COUNTERMEASURES AND 

STRATEGIES 

In-flight countermeasures discussed in this section include 

the following: a) napping on the flight deck (cockpit 

napping); b) taking a break involving change in posture, 

mild physical activity, and increased social 

interaction (activity breaks); c) bunk sleep on long-haul 

and ULR flights; d) in-flight rostering approaches on 

long-haul and ULR flights; and e) increased exposure to 

available flight-deck lighting. While not all are either 

currently sanctioned or even frequently utilized, the list 

is intended to be inclusive and address the gamut of 

possible fatigue countermeasures for pilots operating in 

a restrictive environment acknowledging the need for 

safety and operational effectiveness at all times. 

a. Cockpit Napping 

In situations where some sleep is possible but the 

amount of sleep is limited, napping is the most effective 

nonpharmacological technique for restoring alertness. 

There is an abundance of evidence that a nap taken during 

long periods of otherwise continuous wakefulness 

is extremely beneficial ( 22 , 23 , 74 , 128 , 171 , 174 , 217 , 221 ). 

How ever, while naps can be used as a preventive countermeasure 

in preparation of an upcoming duty schedule 

or during layover periods ( 176 ; see section IV.b.ii), 

cockpit napping is not currently sanctioned by the 

FAA. 

A direct examination of the effectiveness of a 40-min 

cockpit nap opportunity, resulting in an average 26-min 

nap, revealed significant improvements in subsequent 

pilot physiological alertness and psychomotor performance 

( 177 ). Pilots in this study were assigned to either 

a rest group or a no-rest group. The rest group was allowed 

a planned, 40-min nap during a low workload 

portion of the flight. The no-rest group maintained their 

usual flight duties and were not allowed a nap period. 

Physiological data showed more alertness in the rest 

group during the last 90 min of flight than in the no-rest 

group. Reaction time and lapse data (failures to respond) 

from the Psychomotor Vigilance Test (PVT) indicated 

faster responses and fewer lapses in the rest group than 

in the no-rest group. 

These naps virtually eliminated the inadvertent lapses 

in alertness immediately prior to landing present in the 

control group. Furthermore, in-seat cockpit naps have 

been authorized for use in a number of foreign air carriers 

(e.g., Air Canada, Air New Zealand, British Airways, 

Emirates, Finnair, Lufthansa, Swissair, Qantas; 92 ) without 

producing adverse effects. Survey results indicate 

U.S. commercial pilots are, in fact, already utilizing inseat 

cockpit napping strategies. In the NASA regional 

airline operations survey, 56% of flightcrew respondents 

reported they had been on a flight during which arrangements 

had been made for one pilot to sleep in the 

seat during the segment ( 55 ). For flightcrew responding 

to the corporate/executive flight operations fatigue survey, 

the number was 39% ( 175 ). In an earlier long-haul 

study ( 87 ), flightcrew were observed napping 11% of the 

available time with an average duration of 46 min (range: 

10 – 130 min). Finally, according to a National Sleep Foundation 

poll ( 141 ) in which respondents from the general 

public were asked to rate their level of agreement with 

the statement “ An airline pilot who becomes drowsy 

while flying should be allowed to take a nap if another 

qualified pilot is awake and can take over during the 

nap, ” the vast majority of respondents (86%) said that 

they completely or mostly agree with this statement, 

with more than one-half (57%) saying that they completely 

agree. 

b. Activity Breaks 

Short breaks can serve to increase alertness by reducing 

the monotony of a highly automated cockpit environment 

through conscious disengagement with the flying 

task and, possibly, by allowing mild physical activity, 

depending on the type of break and the behaviors allowed 

during the break. Although not as effective as 

some other countermeasures reviewed in this paper, 

there are anecdotal reports from pilots indicating that 



many take brief, out-of-the-seat breaks as a fatigue 

countermeasure. 

Currently, the CFRs mandate a pilot remain seated 

through the flight, with few exceptions. ‡ Nevertheless, 

activity breaks that allow a pilot to change posture by 

getting up out of the cockpit seat and walking or otherwise 

physically moving while engaging in increased social 

interaction can increase alertness levels for brief periods. 

In a study directly addressing the effects of 

in-flight activity breaks, pilots flew a 6-h uneventful 

nighttime flight (~0200 to 0800) in a high-fidelity Boeing 

747-400 flight simulator after having been awake 18 to 

20 h ( 144 ). Pilots in the treatment group were provided 

a 7-min break every hour, at which time they exited the 

simulator and walked to a pilot briefing room where 

they could also engage in conversation with an experimenter. 

The control group received a single break midflight. 

The group that received hourly breaks showed 

significantly less physiological sleepiness up to 15 min 

after the 7-min break and significantly greater subjective 

alertness up to 25 min postbreak. However, performance 

on the psychomotor vigilance task (PVT), taken 

15 min after the break, showed no significant differences. 

Nor were there significant differences in subjective 

alertness and sleepiness 40 min after the break. The 

beneficial subjective and physiological effects of the 

breaks were most pronounced around the low point in 

body temperature (i.e., circadian trough). Matsumoto 

and colleagues showed similar results but volunteers 

were provided a 15-min walking break at a leisurely 

speed ( 129 ). Subjects underwent the same sleep deprivation 

protocol two times: one with light exercise (i.e., 

walking breaks) and the other without exercise. Reductions 

in subjective sleepiness were seen up to 15 min after 

the walking breaks; however, there were no significant 

differences in performance measures. Sleepiness 

ratings were significantly greater when breaks were not 

taken. 

The beneficial effects of breaks are in part due to postural 

changes that occur when a pilot temporarily hands 

off flight-related tasks. There are consistent results from 

laboratory-based sleep deprivation research examining 

the effects of posture. In one study, subjects who underwent 

20 h of continuous wakefulness showed increased 

EEG arousal, decreased reaction times and increased attention 

when completing the PVT while standing, compared 

to when seated ( 49 ). In another total sleep deprivation 

laboratory protocol of 40 h, changes in body 

posture improved alertness levels during the circadian 

trough ( 64 ). 

‡ Note that the Code of Federal Regulation 121.543 specifies that “ … 

Except as provided in paragraph (b) of this section, each required 

flightcrew member on flight deck duty must remain at the assigned 

duty station with seat belt fastened while the aircraft is taking off or 

landing, and while it is enroute. (b) A required flightcrew member 

may leave the assigned duty station - (1) If the crewmember’s absence 

is necessary for the performance of duties in connection with the operation 

of the aircraft; (2) If the crewmember’s absence is in connection 

with physiological needs; or (3) If the crewmember is taking a rest period, 

and relief is provided … ” 

What about a break in which the pilot briefly disengages 

from the flying task (which may involve only 

monitoring instruments) during the cruise portion of 

the flight but does not leave the seat Even if there is no 

associated increase in physical activity, several studies 

indicate an improvement in alertness and performance 

simply associated with a cognitive break from continuous 

tasks. A recently published study evaluated the effects 

of increasing the total break time received by individuals 

performing data entry, a task that can be 

monotonous and boring ( 86 ). Four 5-min supplemental 

breaks were added to the already scheduled two 15-min 

breaks in a workday. The data entry workers were studied 

for 4 wk in each of the break conditions (i.e., 30-min 

total and 50-min total). Results showed the additional 20 

min of break time, incorporated into the workday, was 

associated with significantly faster data entry speeds 

(without a loss of productivity) and reductions in reports 

of physical discomfort. 

Data have shown that breaks also can have positive 

effects when individuals are experiencing partial or total 

sleep loss. In two different total sleep deprivation 

protocols, ranging from 54 h to 64 h of continuous wakefulness, 

individuals who received five 20-min rest breaks 

showed improvements in performance, alertness, fatigue, 

and overall mood when compared to those who 

received no breaks ( 96 ). These beneficial effects also 

translate to actual aviation environments where rest 

breaks have been shown to help military pilots working 

sustained operations overcome increasing sleepiness 

and fatigue levels ( 7 ). 

Whether engaging in a break involving activity or 

simply taking advantage of the opportunity to disengage 

from the current task, the available data suggest 

that the resulting increase in social interaction often accompanying 

a work break can play a role in maintaining 

alertness, especially during the early morning hours 

around the circadian nadir ( 64 ). However, despite substantial 

evidence that breaks are beneficial, it should be 

noted that the findings are not universally positive. For 

instance, in a study of industrial engineers, Tucker, 

Folkard, and Macdonald ( 208 ) found that, following a 

15-min break after 2 h of continuous work, the risk of 

on-the-job mishaps increased approximately linearly 

across the next 2 h such that it doubled during the last 

30-min period of the 2 h. Clearly, the decision whether 

or not to utilize rest breaks must take into account the 

context in which they are being considered, including 

the nature of the task itself. 

c. Bunk Sleep 

It was concluded during the ULR Crew Alertness 

workshops that ensuring adequate bunk sleep is one of 

the most important in-flight countermeasures that can 

be implemented to address sleep loss and circadian disruption 

during extended aviation operations ( 83 ). 

Obtaining sleep addresses the underlying physiology of 

sleep loss and is the only way to reverse cumulative 

sleep debt. Importantly, it is an operationally feasible 



approach to address sleep loss associated with extended 

hours of wakefulness, crossing multiple time zones, and 

flying during nighttime hours. 

In-flight bunk sleep periods can be challenging because 

they need to be scheduled in consideration of operational 

demands and be of a duration that allows all 

crewmembers to receive ample rest periods to ensure 

the safety of the flight. The body is programmed for two 

periods of sleepiness throughout the day with the maximum 

sleep propensity occurring during the early morning 

hours (in the latter half of the habitual sleep episode) 

and a second period of increased sleep propensity occurring 

in midafternoon ( 65 , 213 ). Therefore, crews can 

estimate the times during a flight at which there is an increased 

risk of inadvertent sleepiness, and these are the 

best times (from a circadian standpoint) to schedule inflight 

bunk sleep opportunities. If flight demands permit, 

utilizing these periods of increased physiological 

sleep propensity will help to increase both the quantity 

and quality of bunk sleep, subsequently reducing physiological 

sleepiness across the flight ( 53 , 63 , 65 ). Unfortunately, 

bunk rest periods often unavoidably end up at 

less than optimal times because of a crewmember’s job 

responsibilities. The signal or drive for wakefulness 

from the circadian clock increases throughout the waking 

day with a peak occurring several hours before habitual 

bedtime ( 111 ). Thus, trying to advance sleep initiation 

to a few hours before habitual bedtime will likely 

result in difficulty with sleep initiation and reduced 

sleep duration. 

Research has shown that environmental factors in the 

bunk facilities can help to promote good sleep. A survey 

study conducted by NASA showed that the most common 

factors to interfere with bunk sleep are ambient 

temperature, noise in the galley, and background lighting 

( 179 ). These are all environmental issues that can be 

addressed in the design of bunk facilities. Pilots also indicated 

that making the sleeping quarters more private 

and the use of comfortable bedding and blankets help to 

promote the quantity and quality of their sleep. 

d. In-Flight Rostering 

In-flight rostering, although not commonly discussed 

as a fatigue countermeasure, can be used to minimize fatigue. 

It refers to the scheduling of flightcrew to assigned 

positions on the flight deck, freeing other flightcrew to 

obtain in-flight rest or bunk sleep. In-flight rostering is 

directly related to the crew complement, or number of 

pilots assigned to the flight and is determined — in advance 

— during the scheduling process. Research has 

shown that performance begins to deteriorate after 18 to 

20 h of continuous wakefulness with all aspects of cognitive 

functioning and mood being affected ( 24 ). Also, 

shift worker studies generally indicate that long duty 

hours increase the incidence of physical complaints, the 

use of unhealthy coping behaviors such as smoking and 

poor diet, domestic problems, and possibly musculoskeletal 

disorders. Furthermore, working shifts longer 

than 8 to 9 h is thought to increase the probability of 

having accidents or making errors ( 84 , 198 ). It has been 

shown specifically in aviation that when the “ time since 

awakening ” extends beyond the median for crew position, 

there is an increase in overall errors ( 139 ). Therefore, 

a sufficient number of crewmembers is necessary to provide 

multiple opportunities for rest. 

Proper in-flight rostering can help to minimize extended 

wakefulness and minimize fatigue by ensuring 

that at least one crewmember is always rested. Importantly, 

it allows for scheduling of bunk sleep in a way 

that minimizes the hours of continuous wakefulness for 

the landing pilots and utilizes crewmembers who are 

well rested during other critical phases of flight. However, 

this approach only works if crew rostering is considered 

in the planning stages of the flight, the crew is 

educated about the rostering approach, and the crew adheres 

to the plan during the flight. 

No studies have evaluated, in the context of extended 

aviation operations, the specific number of crewmembers 

needed to ensure adequate sleep opportunities to 

maintain performance and safety. Simply adding crewmembers 

without a sound evidence-based plan of how 

this will improve the situation is not a valid approach. 

Simply providing pilots more opportunity to sleep does 

not ensure they will sleep longer. One study showed 

that when flightcrews were given a 5-h bunk sleep opportunity 

they averaged approximately 3 h ( 97 ). Another 

study found that flightcrews who were provided 

with a 7-h sleep opportunity obtained only 3 h 25 min of 

bunk sleep ( 194 ). 

e. Cockpit Lighting 

Much is now known about the use of properly timed 

bright light to shift human circadian rhythms. The use 

of bright light as an aid to circadian adjustment pre- and 

postflight is discussed in Section IV.b.iii. However, while 

investigated to a lesser extent, light also appears to have 

an acute, immediate, alerting effect on mood and performance 

independent of its circadian phase-shifting properties. 

A recent review of the literature on the acute alerting 

effects of light ( 38 ) shows it to be a potentially useful 

countermeasure at night where conditions allow its use. 

Light’s alerting effects are often believed to be tied to its 

suppression of melatonin, which is ordinarily released in 

the mid to late evening. Hence light has the potential to 

mitigate the usual alertness and performance decline 

seen in the nighttime hours, including on the flight deck. 

How much light is needed Cajochen et al. ( 40 ) showed 

measurable increases in subjective alertness and reductions 

in slow eye movements with room light levels 

(100– 200 lux). Short wavelength light appears to have 

the greatest alerting effect ( 122 ), with the spectrum of 

typical room light containing enough energy in the 

shorter wavelengths to be effective. There is also some 

evidence that the alerting effects of light are independent 

of the time of day, leading to the possibility of employing 

light during the daytime to improve alertness 

and performance in individuals impaired due to prior 

sleep deprivation ( 38 ). 



Capitalizing on the immediate, direct alerting effects of 

light for fatigued flightcrew is particularly appealing because 

the flight-deck environment with its high automation 

level, limited opportunities for physical activity or 

social interaction, steady background noise, and low 

nighttime light levels creates a setting ripe for boredom, 

complacency, attentional lapses, sleepiness, and performance 

decrement. Adjusting the light level is one of a limited 

number of possible environmental manipulations. 

Provided increasing the flight-deck light level at night to 

at least 100 lux (room light level) does not interfere with 

flightcrew performance or visual requirements (e.g., dark 

adaptation level, or ability to see outside the cockpit), 

such light manipulation represents a potentially beneficial 

in-flight countermeasure. While additional research 

is needed to more fully characterize the acute effects of 

light on both daytime and nighttime alertness and performance, 

it should be noted that increasing the light level is 

almost certain to have an effect on circadian phase ( 38 ), 

though it may be slight depending on the timing. 

Position Statement on the Use of In-Flight 

Countermeasures 

All of the in-flight countermeasures described above 

clearly have a place in sustaining the alertness and performance 

of aviation personnel. However, the manner in 

which these strategies are employed should be based on 

the currently available scientific knowledge and should 

be implemented only after thoughtful consideration. 

We recommend the authorized use of in-seat cockpit 

napping in commercial flight operations, under appropriate 

circumstances, with appropriate safeguards, and 

in accordance with clear guidelines to ensure operational 

safety. Cockpit napping should be viewed as a 

risk management tool. Naps have been shown to significantly 

improve alertness and performance in groundbased 

and in-flight studies, and naps can help sustain 

aircrew performance during situations in which unexpected 

delays require the postponement of the next consolidated 

sleep opportunity. In addition, naps can improve 

alertness during circadian low points, especially 

when schedule rotations or rapid time zone transitions 

require that work hours extend into the pilot’s subjective 

nighttime. In-seat cockpit naps have been proven 

safe and effective. However, despite the beneficial effects 

of these naps, they should not be used as a replacement 

for in-flight bunk sleep during long-haul operations. 

Furthermore, in-seat cockpit napping should be 

utilized only when everyone on the flight deck concludes 

that this strategy is necessary to enhance the 

safety of flight operations. The duration of these naps 

should not exceed 40 min in order to avoid excessive 

postnap grogginess (sleep inertia). In a NASA study 

( 177 ), a 40-min nap opportunity resulted in 26 min of actual 

sleep. The short duration of the nap probably minimized 

sleep inertia due to the fact that only 8% of the 

participants reached slow-wave sleep (which has been 

associated with sleep inertia). According to Dinges ( 65 ), 

after 18 h of continuous wakefulness, the latency to slow 

wave sleep is approximately 30 min. Therefore, during a 

nap opportunity of 40 min, it is unlikely most people 

will fall asleep fast enough to obtain more than 30 min 

of sleep, and during that 30 min of sleep, enter into slow 

wave. Other studies have also shown minimal sleep inertia 

effects with naps less than 30 min ( 30 , 204 ). 

We recommend the use of in-flight activity breaks in 

commercial flight operations, under appropriate circumstances, 

with appropriate safeguards, and in accordance 

with clear guidelines to ensure operational safety. 

As with cockpit naps, such breaks should be viewed as 

a risk management tool. In a cockpit environment, which 

can be conducive to sleep, breaks associated with mild 

physical activity and increased social interaction or even 

just temporary disengagement from monotonous tasks, 

have been shown to temporarily boost alertness. When 

using breaks as a fatigue countermeasure, it is recommended 

that shorter breaks (i.e., 10 min) be used hourly 

or more frequently as opposed to longer breaks, which 

can be relatively infrequent. 

The use of bunk sleep and in-flight rostering go handin-hand 

when used as a fatigue mitigation strategy. 

Scheduling practices should always take into account 

the research on both sleep and circadian process when 

scheduling critical phases of flight as well as in-flight 

sleep opportunities. Since the development of the rostering 

pattern should help minimize fatigue during operations, 

policies are necessary to allow for flexibility in 

these rostering approaches if a change, once the flight 

has begun, will contribute to the overall safety of operations. 

Additionally, future applied research is needed to 

determine the optimal timing for crewmembers to obtain 

rest in order to maintain maximum performance 

levels. Operational research evaluating the effects of 

varying crew augmentation options on the efficacy of 

onboard sleep can help address some of these issues. In 

light of the fact that in-flight work/rest planning can be 

a complex matter, it is our position that: 1) aircrews be 

educated with regard to the circadian and environmental 

factors that influence in-flight bunk rest quality; and 

2) when possible, aircrews take advantage of validated 

work/rest scheduling tools to develop the most effective 

in-flight rest pattern given the available crewmembers. 

Lastly, simply increasing the flight-deck light level, 

particularly at night, has the potential to temporarily 

boost alertness and performance. While several light parameters 

and the mechanism of action are still being investigated, 

the beneficial effects have been established 

in several laboratory studies. Any use of light must include 

an awareness of its potential effect on circadian 

phase. 

IV. PRE-/POSTFLIGHT COUNTERMEASURES 

AND STRATEGIES 

a. Hypnotics 

Sleep is often difficult to obtain in operational contexts, 

even in situations where efforts have been made to 

ensure the existence of adequate sleep opportunities. 

There are a number of reasons for this, but generally 



§ Note that at one time, the U.S. Air Force and Army both approved 

the use of triazolam (Halcion w ), but that at present, only the U.S. 

Army continues to authorize the limited use of this medication for 

pre-deployment rest or sustained operations (although in actuality, it 

is rarely prescribed). Triazolam’s purported association with adverse 

effects and its impact on memory have curtailed its use in many clinical 

settings. Therefore, a detailed discussion of triazolam will be omitted 

from the present paper in favor of concentrating on the more frequently 

used hypnotics (temazepam, zolpidem, and zaleplon). 

speaking, the difficulties are due to one or more of the 

following: 1) the sleep environment is less than optimal 

(too noisy, hot, and/or uncomfortable); 2) the state of 

the individual is incompatible with the ability to sleep 

(too much excitement, apprehension, or anxiety); or 3) 

the sleep opportunity occurs at a time that is not biologically 

conducive to rapid sleep onset and/or sufficient 

sleep maintenance. This misalignment of the sleep/ 

wake cycle and endogenous circadian rhythms could be 

the result of shift lag, jet lag, or attempting sleep at other 

than the habitual bedtime or at the second circadian dip 

in the afternoon. For such circumstances, the U.S. Air 

Force and Army have approved the limited use of temazepam, 

zolpidem, and zaleplon. § These hypnotics 

can optimize the quality of crew rest in circumstances 

where sleep is possible, but difficult to obtain. The choice 

of which compound is best for each circumstance must 

take several factors into account, including time of day, 

half-life of the compound, length of the sleep period, 

and the probability of an earlier-than-expected awakening, 

which may increase the risk of sleep inertia effects. 

Temazepam: Temazepam (Restoril w , Euhypnos w , 

Normison w , Remestox w , Norkotral w ) (15 – 30 mg) has 

been recommended in military aviation populations in 

Great Britain since the 1980s ( 150 – 152 ). Given the 

pharmacodynamics of this substance, it may be the 

best choice for optimizing 8-h sleep periods that 

are out-of-phase with the body’s circadian cycle because, 

under these circumstances, sleep is often easy to 

initiate, but difficult to maintain due to the circadian 

rise in alertness. Personnel who work at night generally 

find that they can easily fall asleep after the work 

shift since sleep pressure is high from their previous 

night (and often day) of continuous wakefulness. Also, 

in the early morning, the circadian drive for wakefulness 

is typically low, so the body’s natural rhythms do 

not interfere with sleep onset. However, once daytime 

sleep has begun, night workers are frequently plagued 

by late morning or noontime awakenings that result 

from the increased prominence of circadian-based 

alerting cues. The net result is that the day sleep of 

night workers often is 2 or more hours shorter per day 

than their typical night sleep ( 5 , 205 ). 

For these individuals, the longer half-life of temazepam 

is desirable because the problem usually is one of 

sleep maintenance and not sleep initiation . In addition to 

temazepam’s known facilitation of nighttime sleep 

( 133 , 138 ), this compound, particularly in the 30-mg dose, 

has been shown to objectively and subjectively improve 

daytime sleep as well ( 52 , 153 , 162 ). Temazepam’s intermediate 

half-life of approximately 9 h provides a sufficiently 

lengthy hypnotic effect to mitigate the disruptive 

arousals that often lead to sleep deprivation in personnel 

suffering from shift lag or jet lag. The pharmacokinetic 

disposition of temazepam is affected by the time of 

administration; the absorption of the drug is faster and 

the half-life and distribution are shorter for daytime administration 

compared to nighttime administration 

( 138 ). Furthermore, in studies involving simulated night 

operations, temazepam has been shown to improve 

nighttime performance by optimizing daytime sleep 

( 162 ). A study using U.S. Army pilots who worked and 

flew at night in a simulated shift-work environment 

demonstrated that temazepam-induced improvements 

in daytime sleep led to better nighttime pilot performance 

(relative to placebo) as well as improvements in 

psychomotor vigilance and self-reported alertness ( 52 ). 

Thus, temazepam appears to be a good choice for 

maximizing the restorative value of daytime sleep opportunities. 

However, caution should be exercised prior 

to using temazepam in certain operational settings since 

the compound does have a relatively long half-life. Although 

residual effects were not reported in a military 

study in which personnel were able to gain suitable 

sleep before reporting for duty ( 29 ), nor in some other 

situations in which 30 – 40 mg of temazepam were given 

prior to a full sleep opportunity ( 180 , 227 ), residual postdose 

drowsiness has been reported elsewhere. Paul, 

Gray, MacLellan, and Pigeau ( 158 ) observed that drowsiness 

was noticeable within 1.25 and 4.25 h of a midmorning 

15-mg dose. They also noted that psychomotor 

performance was impaired between 2.25 and 4.25 h 

postdose (plasma levels were still elevated at 7 h postdose). 

These data suggest the possibility that temazepam’s 

long half-life could exacerbate sleep inertia upon 

awakening; however, the potential for this drawback 

must be weighed against the potential for impairment 

from sleep truncation in the event that temazepam therapy 

is withheld. Along these lines, it should be noted 

that Roehrs, Burduvali, Bonahoom, Drake, and Roth 

( 170 ) found that just 2 h of sleep loss produces the same 

level of sedative effect as the consumption of 0.54 g/kg 

of ethanol (the equivalent of 2 to 3 12-oz bottles of beer), 

whereas the effects of 4 h of sleep loss are similar to those 

of 1.0 g/kg of ethanol (5 to 6 12-oz beers). Other investigations 

have similarly shown that sleep restriction and 

sleep deprivation degrade performance as much as, or 

more than, alcohol intoxication. 

The same qualities that make temazepam desirable 

for maintaining the daytime sleep of shift workers make 

it a good choice for temporarily augmenting the nighttime 

sleep of personnel who are deployed westward 

across as many as nine time zones ( 149 , 201 ). Upon arrival 

at their destination, these travelers are essentially 

facing the same sleep/wake problems as the night 

worker. Namely, they are able to fall asleep quickly since 

their local bedtime in the new time zone is much later 

than the one established by their circadian clock (from 

the origination time zone); however, they generally are 

unable to sleep throughout the night. The reason for this 



is demonstrated by the following example: a 6-h westward 

time zone change places bed time at 2300 local 

time which is 0500 origination time; this is followed by a 

wakeup time of 0600 local which corresponds to a 

“ body-clock time, ” still adjusted to the origination time, 

of 1200. Based on a readjustment rate of 1.5 d per time 

zone crossed ( 105 ), it could take up to a week for adjustment 

to the new time zone to occur. Until this adjustment 

is accomplished, temazepam can support adequate 

sleep maintenance despite conflicting circadian signals 

and the obvious benefit will be less performancedegrading 

sleep restriction. While the problem with 

daytime alertness due to circadian disruptions will not 

be alleviated, the daytime drowsiness associated with 

increased homeostatic sleep pressure (from sleep restriction) 

will be attenuated. 

Thus, temazepam is a good choice when a prolonged 

hypnotic effect is desired as long as there is relative certainty 

that the hypnotic-induced sleep period will not be 

unexpectedly truncated. This compound is especially 

useful for promoting optimal sleep in personnel suffering 

from premature awakenings due to shift lag or jet 

lag since the hypnotic effect helps to overcome circadian 

factors that can disrupt sleep immediately following a 

time zone or schedule change. However, temazepam 

should not be used longer than is necessary to facilitate 

adjustment to the new schedule. Depending on the circumstances, 

temazepam therapy probably should be 

discontinued after 3 to 7 d either to prevent problems 

associated with tolerance or dependence (in the case of 

night workers) or because adjustment to the new time 

zone should be nearly complete (in the case of travelers 

or deployed personnel) ( 149 ). When discontinuing temazepam 

after several continuous days of therapy, it is 

recommended that the dosage be gradually reduced for 

2 to 3 d prior to complete discontinuation in order to 

minimize the possibility of rebound insomnia ( 181 , 209 ). 

Zolpidem: Zolpidem (Ambien w , Stilnox w , Myslee w ) 

(5 – 10 mg) may be the optimal choice for sleep periods 

less than 8 h, and zolpidem would be a better choice 

than temazepam if there were a possibility that the 

hypnotic-induced sleep period is likely to be unexpectedly 

shortened. This compound is especially useful for 

promoting short- to moderate-length sleep durations (of 

4 to 7 h) when these shorter sleep opportunities occur at 

times that are not naturally conducive to sleep. As noted 

above, daytime naps would fall into this category because, 

just like daytime sleep in general, daytime naps 

are typically difficult to maintain ( 61 , 111 , 205 ), especially 

in non-sleep-deprived individuals. Furthermore, unless 

the naps are placed early in the morning or shortly after 

noon, they can be extremely difficult to initiate without 

some type of pharmacological assistance ( 89 ). Zolpidem 

is a good choice for facilitating such naps because its relatively 

short half-life of 2.5 h provides short-term sleep 

promotion while minimizing the possibility of postnap 

hangovers. Thus, it is feasible to take advantage of a nap 

without significantly lengthening the postnap time 

needed to ensure that any drug effects have dissipated. 

However, as with temazepam, there should be a reasonable 

degree of certainty that there will not be an early interruption 

of the sleep period followed by an immediate 

demand for performance. 

The efficacy of zolpidem as a nighttime sleep promoter 

has been clearly demonstrated in clinical trials 

(with up to 1 yr of administration) in normal, elderly, 

and psychiatric patient populations with insomnia ( 21 ). 

Rebound insomnia, tolerance (treatment over 6 to 12 

mo), withdrawal symptoms, and drug interactions are 

absent, and the dependence/abuse potential is low ( 16 ). 

Overall, zolpidem is a clinically safe and useful hypnotic 

drug ( 156 , 188 ). 

Zolpidem has been proven to possess utility in militarily 

relevant circumstances. An Army study ( 43 ) demonstrated 

that zolpidem-induced prophylactic naps enhanced 

the alertness and performance of sleep-deprived 

pilots (relative to placebo) during the final 20 h of a 38-h 

period of continuous wakefulness without producing 

significant hangover effects. Since these naps were 

placed at a time during which sleep is often difficult to 

obtain ( 111 ), the benefits in terms of sleep promotion 

and sleep quality were clear. Thus, zolpidem is an effective 

way to promote short naps, and, relative to placebo, 

is associated with improved subsequent alertness. 

Zolpidem may also be helpful for promoting the sleep 

of personnel who have traveled eastward across 3 to 9 

time zones ( 202 ). Unlike westward travelers who experience 

sleep maintenance difficulties, eastward-bound personnel 

suffer from sleep initiation problems. For example, 

a 6-h time zone change in the eastward direction 

creates difficulty with initiating sleep because a local 

bedtime of 2300 translates to a body clock time of only 

1700, and it has been well established that such early 

sleep initiation is problematic ( 150 , 201 , 219 ). Thus, eastward 

travelers need something that will facilitate early 

sleep onset and suitable sleep maintenance until the 

normal circadian-driven sleep phase takes over; however, 

they do not need a compound with a long half life. 

This is because, in this example, any residual drug effect 

would only exacerbate the difficulty associated with 

awakening at a local time of 0700 that corresponds to an 

origination time (or body-clock time) of only 0100 in the 

morning. As stated above, sleep difficulties are only part 

of the jet-lag syndrome, but alleviating sleep restriction 

or sleep disruption will help to attenuate the alertness 

and performance problems associated with jet lag. 

Thus, zolpidem is a good compound for facilitating 

naps of moderate durations (4 to 7 h), even when these 

naps occur under less-than-optimal circumstance and/ 

or at the “ wrong ” circadian time. Zolpidem is also appropriate 

for treating sleep-onset difficulties in eastward 

travelers. However, as is the case with any hypnotic, this 

medication normally should be used only when necessary, 

i.e., prior to circadian adjustment to a new work or 

sleep schedule. More chronic zolpidem administration 

may be essential for promoting naps that occur under 

uncomfortable conditions or naps that are “ out of phase ” 

since, by definition, these generally are difficult to initiate 

and maintain, but zolpidem probably should not be 

used for more than 7 d to counter insomnia from jet lag. 



After this time, most of the adjustment to the new time 

zone should be accomplished ( 201 , 219 ). 

Zaleplon: Zaleplon (Sonata w , Starnoc w ) (5 – 10 mg) 

may be the best choice for initiating very short naps (1 to 

2 h) during a period of otherwise sustained wakefulness 

or for initiating early sleep onsets in personnel who are 

trying to ensure sufficient sleep prior to a very early 

start time the next morning. With regard to facilitating 

early report times, zaleplon is an option to zolpidem, 

but both compounds are important for the same reason. 

As noted earlier, it is extremely difficult for most people 

to initiate sleep 1 to 4 h prior to their typical bedtimes 

unless they are severely fatigued ( 6 , 90 , 111 ). Since these 

individuals are unable to fall asleep early, the total length 

of their sleep period is truncated by the early rise time 

even if, once they finally go to sleep, they sleep relatively 

well. Personnel who are required to report to duty in the 

predawn hours can easily suffer 2 to 3 h of sleep deprivation 

because of physiologically based sleep initiation 

difficulties. This is why short-haul pilots attribute a substantial 

percentage of their fatigue-related problems to 

early report for duty times ( 28 ). Sleep truncation of this 

amount has been shown to significantly impair both 

alertness and performance ( 17 , 162 , 214 ). Similar to zolpidem 

(which has a 2.5-h half-life), zaleplon can overcome 

this sleep initiation problem, and its ultra-short 1-h half 

life is less likely to pose hazards in terms of residual 

drug effects that can exacerbate the drowsiness associated 

with the predawn awakening dictated by the early 

start time. 

Clinical trials of the hypnotic efficacy of zaleplon have 

shown improvement in sleep initiation, particularly 

with the 20-mg dose ( 54 , 80 , 85 ). In people diagnosed with 

primary insomnia, the latency to sleep onset decreased 

significantly compared to placebo ( 54 ). After zaleplon 

exerts its initial effects, the drug is subsequently (and 

quickly) eliminated in time for more natural physiological 

mechanisms to take over and maintain the remainder 

of the sleep period. There is evidence that there are 

no hangover problems as early as 6 to 7 h later ( 54 ). The 

rapid initiation of sleep at an earlier-than-normal time 

permits a full sleep period despite the requirement for 

an early awakening, and thus bolsters subsequent performance. 

Paul et al. ( 157 ) found that 10 mg zaleplon 

impaired psychomotor performance for up to 2.25 h after 

ingestion. The same dose increased drowsiness from 

2 to 5 h after dosing ( 158 ), with plasma drug levels equal 

to placebo by 5 h postdose. These authors recommend 

zaleplon for times when an individual may have to 

awaken no earlier than 3 h after drug ingestion. 

Thus, zaleplon (10 mg) is a good hypnotic for promoting 

short naps (2 to 4 h) which would otherwise be difficult 

to initiate and maintain, as well as for hastening the 

early-to-bed sleep onset of personnel who are faced with 

an acute demand to report for duty in the early morning 

(i.e., at 0400 to 0500). In addition, as was the case with zolpidem, 

zaleplon can be considered useful for the treatment 

of sleep-onset insomnia in eastward travelers who 

are experiencing mild cases of jet lag. For instance, those 

who have transitioned eastward only 3 to 4 time zones can 

use this short-acting drug to initiate and maintain what 

the body believes to be an early sleep period. As with any 

hypnotic, the course of treatment should be kept as short 

as reasonably possible to minimize drug tolerance and 

drug dependence (149 ). Table II summarizes some of the 

characteristics of each of the hypnotics discussed. 

Newer hypnotics: Some of the newer hypnotics available 

help with sleep maintenance without the extended 

long half-life of temazepam. For example, the extendedrelease 

zolpidem (Ambien CR w ) improves sleep maintenance 

beyond that of zolpidem ( 93 ). In addition, eszopiclone 

( Lunesta w ) has a half-life of 5 to 6 h with minimal 

residual drug effects after as little as 10 h post dose ( 114 ). 

Ramelteon (Rozerem w ) is a novel hypnotic in that it targets 

the melatonin receptors in the brain in order to regulate 

the body’s sleep-wake cycle ( 119 ). Research indicates 

that this drug is efficacious for sleep onset, but not 

for sleep maintenance ( 119 ). 

New sleep-promoting compounds are being produced 

by the pharmaceutical industry each year. One hypnotic 

slated to come on the market in the near future is indiplon. 

This drug is similar in structure to zaleplon and 

has a half-life of approximately 1.5 h; it is also being formulated 

with a modified release as well which will extend 

its half-life to aid in sleep maintenance ( 79 ). There 

are new compounds which are rapidly absorbed and 

Generic name Brand Name Dosage 

Temazepam 

Zolpidem 

Zaleplon 

Restoril w 

Euhypnos w 

Normison w 

Remestox w 

Norkotral w 

Ambien w 

Stilnox w 

Myslee w 

Sonata w 

Starnoc w 

TABLE II. LIST OF HYPNOTICS AND THEIR USES. 

Average 

Half-life Recommended Use Cautions 

15 – 30 mg 9 h Sleep maintenance; daytime sleep; 

prolonging sleep to avoid early 

morning awakenings from jet lag/shift lag 

5 – 10 mg 2.5 h Sleep initiation; intermediate-length naps; 

assisting early sleep onset due to early 

bedtimes from shift or time zone change 

5 – 10 mg 1 h Sleep initiation; short naps; assisting early 

sleep onset due to early bedtimes from 

shift or time zone change 

Need an 8-h sleep 

period; not recommended 

if on-call 

Need to have at least 4-6 h of 

sleep; not recommended 

if on-call 

Not recommended if 

on-call 



have a short half-life, and some have the ability to increase 

both slow-wave sleep and slow-wave activity, 

which improves sleep efficiency. These compounds may 

improve sleep efficiency to the point that effective wakefulness 

can be sustained on fewer than the 8 h of daily 

sleep that is now required. Perhaps short power naps of 

3 to 4 h could become equally effective, but research remains 

to substantiate this possibility. 

Current civilian aviation policy allows limited use of 

zolpidem only. The FAA allows its use no more than 

twice a week, and states that it cannot be used for circadian 

adjustment. In addition, there is a 24-h grounding 

policy for any pilot who uses zolpidem. While melatonin 

is not a prescription hypnotic medication in the United 

States, it is a controlled substance in many other countries. 

The use of melatonin to promote sleep is discussed 

in a later section on nonpharmacological substances. 

Sleep promoting compounds can be useful in operational 

contexts where there are problems with sleep initiation 

or sleep maintenance. However, it should be 

noted that, like all medications, there are both benefits 

and risks associated with the use of these compounds. 

These should be considered by the prescribing physician 

and the individual pilot before the decision to utilize 

hypnotic therapy is finalized. A hypnotic of any 

type probably should not be used if the crewmember is 

likely to be called back to duty earlier than anticipated 

because this would put them at risk of performing flight 

duties before the medication has been fully metabolized. 

Although temazepam, zolpidem, and zaleplon 

are widely recognized as being both safe and effective, 

personnel should be cautioned about potential side effects 

and instructed to bring these to the attention of 

their physician should they occur. Potential problems 

may include morning hangover, which may cause detrimental 

effects on performance, dizziness, and amnesia 

that may be associated with awakenings that are forced 

before the drug has been eliminated, and various idiosyncratic 

effects ( 14 , 131 , 149 , 181 ). If any difficulties occur, 

it may be necessary to discontinue the specific compound 

or to abandon hypnotic therapy altogether. 

However, it is likely that significant side effects can be 

reduced or eliminated by using the correct compound 

or by modifying dosages or dose intervals ( 150 ). For 

these reasons, military personnel are required to receive 

a test dose of the hypnotic of interest under medical supervision 

before using the medication during operational 

situations. Even after the test dose yields favorable 

results and it is clear that operationally important 

side effects are absent, hypnotics should be used with 

particular caution when the aim is to aid in advancing 

or delaying circadian rhythms in response to time zone 

shifts ( 149 , 201 , 219 ). Reviews by Waterhouse and associates 

( 219 ), Nicholson ( 149 ), and Stone and Turner ( 201 ) 

offer detailed information on this rather complex 

issue. 

While the use of sleep aids is authorized in both civilian 

and military aviation, the restrictions in the civilian 

community are such that pilots do not receive the intended 

benefits of their use. The policy that hypnotics 

not be used for circadian disruption is overly restrictive 

since it is precisely for this reason that hypnotics would 

be useful for pilots crossing multiple time zones or flying 

early morning flights. The policy adopted by the 

military community allows the use of hypnotics with 

specified grounding times, allowing pilots to obtain restful 

sleep prior to a difficult schedule, but such that hypnotic 

use does not interfere with flight times. It would be 

useful for the civilian community to evaluate the hypnotic 

policy implemented by the military to allow safe 

use of hypnotics by civilian pilots. Education concerning 

the appropriate use of hypnotics, along with relevant 

grounding periods, would allow pilots to obtain sleep 

which may not otherwise occur. Also, by allowing a 

choice of hypnotics rather than allowing only one, a variety 

of hypnotics with varying length of action will allow 

the appropriate drug for the specific time of use. 

Position Statement on the Use of Hypnotics 

For the present time, it is our position that zolpidem 

be authorized for civilian commercial pilots a maximum 

of 4 times per week in situations where natural sleep is 

difficult or impossible due to circadian or other reasons 

provided that: 1) the pilot has checked for any unusual 

reactions to the medication during an off-duty period; 2) 

the dose does not exceed 10 mg in any given 24-h period; 

and 3) there is a minimal interval of 12 h between 

the ingestion of the medication and the return to duty. 

This recommendation is based on research which shows 

that: 1) zolpidem’s half-life of 2.5 h (extended release 

half-life is 2.8 h) allows it to be fully metabolized in 10 h 

(11.2 h for extended release); and 2) research has shown 

that repeated use of zolpidem in clinical settings continuously 

improves sleep quality without causing rebound 

insomnia or exerting a negative impact on next day 

alertness ( 107 ). Zolpidem should not be taken to promote 

any type of in-flight sleep. It should be noted that 

facilitating quality sleep with the use of a well-tested, 

safe pharmacological compound is far better than having 

pilots return to duty when sleep deprived or having 

them return to duty following a sleep episode that has 

been induced with alcohol. Studies have shown that despite 

the “ 8-h bottle-to-throttle ” rule, impairments due 

to even moderate alcohol consumption may persist 

throughout the night to the morning after ( 234 ). 

b. Improving Sleep and Alertness 

This section describes improving pre- and postflight 

sleep and alertness without the use of medications or 

pharmacological countermeasures. Such countermeasures 

are discussed in the context of military aviation 

(see Section VI.) where they are currently permitted under 

specified circumstances and with specified controls. 

i. Healthy Sleep Practices: Whenever possible, getting a 

sufficient quantity of high quality sleep on a daily basis 

must be the number one focus in fighting fatigue. How 

much is sufficient Generally speaking, people require 

about 8 h of sleep per day in order to sustain optimum 

alertness ( 222 ). Although some people can function well 



on less, they are small in number. Two strategies can 

help determine individual sleep need. 

The first strategy is to extend the nightly sleep period 

an extra hour over the course of the next 7 d, and after 

the 7th d, self-reflect on whether the additional sleep has 

been beneficial in terms of cognitive performance, mood, 

and alertness. The second, and more reliable, strategy is 

to keep a sleep diary during the next vacation when it is 

possible to sleep ad lib for several days. After recording 

the time of natural sleep onset and natural awakening 

(without the aid of an alarm clock) for 5 to 7 d (excluding 

the first 2 vacation days), obtain the average sleep 

time and make this amount of sleep each night the goal 

upon returning to work. 

Obtaining the required quantity of sleep on a day-today 

basis obviously is important, but obtaining high 

quality sleep is beneficial as well. Sleep fragmentation 

is known to degrade memory, reaction time, vigilance, 

and mood ( 25 ). Specific strategies can help optimize 

each sleep opportunity, and these are presented 

below. 

Strategies for Optimizing Sleep Opportunities: 

• When possible, wake up and go to bed at the same time every 

day to avoid circadian disruptions. 

• Use the sleeping quarters only for sleep and not for work. 

• If possible, establish a consistent and comforting bedtime routine 

(e.g., reading, taking a hot shower, and then going to 

bed). 

• Perform aerobic exercise every day, but not within 2 h of going 

to bed. 

• Make sure the sleeping quarters are quiet, totally dark, and 

comfortable. For this to work, day workers should be housed 

separately from night workers. 

• Keep the sleep environment cool (~26 ° C if you are covered). 

• Move the alarm clock out of sight so you can’t be a clock 

watcher. 

• Avoid caffeine in drinks and other forms during the 

afternoons/evenings. 

• Don’t use alcohol as a sleep aid (it may make you sleepy, but 

you won’t sleep well). 

• Avoid cigarettes or other sources of nicotine right before 

bedtime. 

• Don’t lie in bed awake if you don’t fall asleep within 30 min – 

instead, leave the bedroom and do something relaxing and 

quiet until you are sleepy. 

ii. Napping: In employing a napping strategy pre/ 

postflight, an important factor is nap timing or placement. 

A nap taken during the day before an all-night 

work shift (a prophylactic nap), with no sleep loss 

prior to the shift, will result in improved performance 

over the night compared to performance without the 

nap ( 23 , 191 ). Although naps taken later in the sleepdeprivation 

period also are beneficial, these naps probably 

should be longer than prophylactic naps in order 

to derive the same performance benefit. Schweitzer et 

al. ( 191 ) demonstrated that when subjects received a 2- 

to 3-h nap before a night work shift (with concurrent 

sleep loss) they performed better than when receiving 

no nap. Bonnet ( 23 ) showed that a nap before a 52-h 

continuous performance period was beneficial in keeping 

performance and alertness from decreasing for up 

to 24 h compared to the no-nap condition, but by the 

second night of sleep loss, the benefit of the naps could 

not be reliably measured. 

Another important factor is nap length . A relationship 

between nap length and performance was reported by 

Bonnet ( 23 ) based on a study in which subjects were allowed 

either a 2-, 4-, or 8-h nap before 52 h of continuous 

operations. The results indicated a dose-response relationship 

between the length of the nap and performance 

during the first 24 h of sleep deprivation. Bonnet concluded 

that the nap before an all-night shift should be as 

long as possible to produce maximum performance benefits 

and that prophylactic naps were better than naps 

designed to replace sleep that was already lost due to 

the requirement for continuous wakefulness. This conclusion 

was supported in a study by Brooks and Lack 

( 30 ), who tested afternoon naps of 5, 10, 20, and 30 min 

following nighttime sleep of 5 h. The longer 20- and 30- 

min naps showed improvement in overall cognitive performance 

for as long as 155 min compared to the 10-min 

nap which showed cognitive performance effects for 

only 95 min. This finding is consistent with a recent 

meta-analysis on the efficacy of naps as a fatigue countermeasure 

( 75 ). This meta-analysis of 12 studies consisting 

of a total of 178 tests not only concluded that 

naps led to performance benefits equal to, and sometimes 

greater than, baseline performance levels, but also 

that the length of performance benefit was directly proportional 

to the length of the nap (e.g., a 15-min nap led 

to 2 h of benefit while a 4-h nap led to 10 h of benefit). 

However, it was also noted that, regardless of nap length, 

the performance benefit decreased as postnap interval 

increased (i.e., the benefits of a 4-h nap were greater 

shortly after awakening than after 10 h, though performance 

at the later time still met or exceeded baseline 

performance). 

A final consideration is the placement of the nap with 

regard to the phase of the body clock (circadian phase). Nap 

timing should take into account the impact of circadian 

phase on sleep propensity, structure, and quality across 

the day as well as the effects on performance both immediately 

after awakening and later in the work period. 

Sleep tendency is highest during the daily trough in 

core body temperature (in the predawn and early morning 

hours) and lowest when core body temperature 

peaks (in the early evening hours) ( 65 ). Thus, there may 

be significant problems initiating and/or maintaining a 

nap during an adverse circadian phase when core temperature 

is near its peak, as during the “ forbidden zone 

for sleep ” a couple of hours prior to habitual bedtime 

( 111 ). Naps placed during the circadian troughs are the 

easiest to maintain and they show beneficial effects on 

later performance. Gillberg ( 89 ) showed that a 1-h nap 

placed at 0430 (in the circadian trough) was more beneficial 

to next-day performance than one placed at 2100. 

However, while naps during the circadian trough may 

be more effective for performance sustainment, they 

also are the more difficult naps from which to awaken. 

Generally, studies have shown that postnap sleepiness, 

termed “ sleep inertia, ” is higher and performance is 

lower immediately upon awakening from a nap taken 

during the circadian trough as compared to naps taken 

during the circadian peak ( 71 ). For this reason, some 



authors suggest that naps in the circadian trough should 

be avoided, and naps should be taken before a person’s 

sleep loss extends beyond 36 h. However, it should be 

possible to take advantage of the improved quality of 

naps in the circadian trough while avoiding the negative 

sleep-inertia effects if napping personnel can be 

awakened about 1 h prior to their work shifts. This will 

allow time to overcome most of the effects of sleep 

inertia. 

iii. Circadian Adjustment: The circadian clock cannot 

adapt immediately to a change in the duty/rest cycle or 

changes in environmental cues, such as those experienced 

with transmeridien travel ( 106 ). When crossing time 

zones, the circadian clock is out of sync with the local environment. 

Adjustment is usually faster after traveling in 

the westward than the eastward direction ( 27 , 185 ). 

Adjustment depends on direction of travel, the number of 

time zones crossed, the rhythm being measured and an 

individual’s exposure to time cues (e.g., light/dark cycle). 

Adjustment does not appear to be linear and those who 

are evening types ( “ owls ” ) tend to adjust to the new time 

zone more quickly relative to morning types ( “ larks ” ). 

Aircrew fatigue resulting from circadian disruption is 

subject to partial alleviation with hypnotics; however, in 

cases where the crewmember will remain in the new 

time zone on a consistent duty schedule for several consecutive 

days, it may be better to restore the body’s natural 

sleep/wake rhythm through other circadian reentrainment 

techniques. Adjusting to new time zones or 

work schedules is largely a matter of controlling exposure 

to sunlight, placing meals and activities at appropriate 

times, and making every effort to optimize sleep 

during available sleep periods ( 11 , 33 , 196 , 220 ). Although 

operational requirements often make it difficult, aircrew 

should pay close attention to their behaviors following 

schedule changes. Several of the recommendations that 

are typically made to help industrial shiftworkers are 

also useful in aviation settings. 

Recommendations for Rotating to Different Shift Schedules: 

• When remaining within the same time zone but rotating to 

night duty, avoid morning sunlight by wearing dark glasses and 

by staying indoors as much as possible prior to sleeping. 

• For daytime sleep, make sure the sleep environment is dark and 

cool. 

• For daytime sleep, use eye masks and earplugs (or a masking 

noise like a box fan) to minimize light and noise interference. 

• For daytime sleep, make sure to implement the good sleep habits 

discussed previously. 

• When on duty at night, try to take a short nap before reporting 

for duty. 

• After waking from daytime sleep, get at least 2 h of sunlight (or 

artificial bright light) in the late afternoon or early evening if 

possible. 

When traveling to a new time, crews will face circadian 

disruptions similar to those encountered by people 

rotating from day shift to night shift within the same 

time zone. Upon arrival in the new time zone (assuming 

that this will be the new duty location for several days, 

weeks, or months and that crewmembers will be flying/ 

working in the daytime rather than at night), the following 

recommendations are available to aid in adjusting to 

new time zones. 

Recommendations for Time Zone Adjustments: 

• Quickly adjust meal, activity, and sleep times to the new time 

zone schedule . 

• Maximize sunlight exposure during the first part of the day. 

• Minimize sunlight exposure during the afternoons. 

• Avoid heavy meals at night because stomach discomfort will 

disrupt sleep. 

• Follow good sleep habit recommendations to optimize nighttime 

sleep. 

• Try self-administered relaxation techniques to promote nighttime 

sleep. 

• If possible, prior to bed time, take a hot bath. Cooling off afterwards 

may mimic the circadian-related temperature reduction 

that normally occurs during sleep. 

• During the first few days of circadian adjustment, use sleep 

medications (if authorized) to promote sleep at night, and use 

caffeine to augment alertness during the day. 

Properly timed bright light is an alternative strategy 

for resynchronizing circadian rhythms after schedule 

changes ( 62 , 88 , 185 ). Several researchers have published 

recommendations about the use of light to promote circadian 

adjustment, but they have pointed out difficulties 

associated with the correct timing of administration 

of light therapy as well ( 77 , 117 , 168 ). Consensus reports 

summarizing issues related to the use of bright light as a 

treatment for jet lag and shift lag also have been published 

( 27 , 78 ). 

Unfortunately, the difficulties associated with appropriate 

timing of artificial bright light therapy often leave 

experts to recommend a reliance on other approaches. In 

addition, it is often difficult to establish any type of 

bright light facility on the ground much less on board 

aircraft. Finally, an approximate understanding of one’s 

circadian status is a prerequisite for phase changes with 

supplementary melatonin. Self-administration techniques 

such as natural sunlight exposure, appropriately 

timed naps, and proper exposure to zeitgebers (time 

cues) may facilitate circadian adjustment to new duty or 

time zone schedules ( 154 , 167 , 201 , 219 ). 

iv. Exercise: Exercise has been shown to be an effective 

fatigue countermeasure in both the laboratory and aviation 

environments. Those who exercise regularly actually 

show improved sleep quantity and quality ( 199 ). 

However, if engaged in too close to bedtime, exercise can 

have negative effects on sleep, making it more disrupted 

( 137 ). Exercise increases physiological arousal and can 

help promote alertness in the short-term. However, it is 

important to consider the level of exercise and the timing 

when determining its effectiveness as a countermeasure. 

Research has suggested that only heavy exercise 

(70%VO 2max ) results in changes in objective vigilance 

performance, and the effects last no longer than 30 min 

( 98 ). These heavy exercise periods were brief (10 min) 

because if too long (~1 h), they would actually increase 

fatigue and sleepiness levels. When exercise levels were 

in the light to moderate range, subjects seemed to be 

more alert and less sleepy for up to a 15-min postexercise 

period. However, more recent research has shown that 

If persons who have been working nights in the U.S. will be working 

days in Europe, it might not be necessary to readjust the body 

clock since it already will be on the proper schedule. 



the subjective effects of moderate exercise bouts can last 

up to 30 min ( 113 ). Subjects who engaged in 10 min of 

moderate exercise every 2 h throughout a 40-h sleep deprivation 

protocol showed less subjective sleepiness up 

to 30 min after exercising. Similar to other research, no 

differences were seen in objective performance. 

While exercise can be used as a fatigue countermeasure 

to improve alertness levels in the short term, it can 

also induce phase shifts in the melatonin circadian 

rhythm and the circadian clock ( 35 , 78 ). Data collected 

by Shiota and colleagues on airline crewmembers flying 

a 4-d flight pattern between Tokyo and Los Angeles 

(8-h time difference) showed that moderate to heavy 

exercise (both in origin and destination cities) helped 

the pilots adapt to the local time zone ( 193 ). This conclusion 

was based on subjective sleep/wake diaries, 

subjective sleepiness levels, and urine excretion of 

17-hydroxycorticosteroids; however, due to data being 

collected during operations, there was no way to conclude 

that it was the exercise alone that helped resynchronize 

the individuals to the new environment. Since 

then, controlled studies have evaluated the ability of 

exercise to shift circadian rhythms ( 99 ). Barger and colleagues 

have evaluated exercise and its effect on circadian 

rhythms in a controlled environment in which light 

was held at a constant dim level ( 15 ). The data showed 

that over a 15-d trial, exercise of appropriately timed duration 

and amount (three 45-min nightly periods), altered 

the volunteers ’ melatonin profiles. Thus, the outcomes 

suggest that exercise can be helpful in facilitating 

a delay of the sleep/wake cycle which is experienced 

during westbound travel. 

v. Nutrition: While eating a meal immediately before 

the sleep period is not recommended, it is important to 

maintain good nutrition. If personnel eat immediately 

before sleep, they should favor grains, breads, pastas, 

vegetables, and/or fruits. At the same time, personnel 

should avoid large meals, high-fat meals, high-acid 

meals, sweets, and significant hunger. 

Normal variations in nutrition have few, if any, major 

effects on sleep structure ( 123 , 146 ). However, dietary 

supplementation and unusual variations in diet may 

have mild effects. For example, high carbohydrate 

(CHO) supplementation prior to bedtime has been associated 

with reduced amounts of wakefulness and stage 

1 sleep, decreased stage 4 sleep, and increased rapid eye 

movement (REM) sleep ( 164 ). The somnolent effects of 

high CHO meals may depend in part on gender, age, 

and time of day of consumption ( 197 ). A CHO lunch has 

been shown to increase the length of a siesta ( 236 ). Recently, 

it was observed that a 90% CHO meal with a high 

glycemic index (GI) shortened sleep latency by about 

50% compared to a low glycemic index meal, and about 

40% when fed 4 h prior to sleep onset compared to 1 h 

before ( 4 ). Conversely, drowsiness may be offset immediately 

after high- and low-GI CHO intake, but low-GI 

CHO intake may delay the onset of drowsiness ( 110 ). A 

comparison of low-fat, high-CHO meals to high-fat, 

low-CHO meals indicated that higher cholecystokinin 

(CCK) concentrations after high-fat, low-CHO meals 

were associated with greater feelings of sleepiness and 

fatigue ( 224 ). 

The essential amino acid, tryptophan, is a precursor of 

the monoamine neurotransmitter serotonin. Serotonin is 

involved in the regulation of sleeping and waking ( 163 ). 

The presleep ingestion of an amino-acid mixture lacking 

tryptophan, compared to the ingestion of a mixture containing 

all essential amino acids, caused a decrease in 

stage 4 sleep latency and an increase in stage 4 sleep 

during the first 3 h of sleep ( 135 ). Depletion has also 

been observed to decrease stage 2 sleep, to increase wake 

time after sleep onset and rapid eye movement density, 

and to shorten the first and second REM period intervals 

( 218 ). Midmorning tryptophan depletion delays 

REM sleep latency during the following night’s sleep 

( 10 ). 

Thus, it appears that the purposeful manipulation of 

dietary CHO by aircrew to help induce and sustain their 

sleep periods may be ill-advised due to the unpredictability 

of effects. However, tryptophan depletion should 

probably be avoided. Obviously, those prone to gastric 

reflux disorders should avoid large or high-fat meals before 

bedtime. 

The failure to eat may trigger sleep disruption and fatigue. 

Low blood glucose may elevate plasma glucagon, 

with concomitant elevations of heart rate, and blood pressure. 

This is not conducive to restful sleep. Of course, hypoglycemia 

can lead to poor cognitive performance. Studies 

of the effects of intermittent fasting during Ramadan 

have revealed increased nocturnal sleep latency, decreased 

daytime sleep latencies, and decreased total sleep time. 

These effects may be dependent upon the late dinners ingested 

during Ramadan ( 172 , 173 ). 

Position Statement on Improving Sleep and Alertness 

A number of alertness-enhancing strategies are available 

that do not rely on medications of any type. 

Whenever possible, these should be applied during offduty 

periods to maximize the safety of flight operations. 

Promoting quality preduty sleep is essential for ensuring 

optimal flight performance. Since healthy sleep 

practices ensure that crews will be able to make the most 

of available sleep opportunities, all aircrew members 

should be provided with educational materials that outline 

natural sleep-promoting behaviors. In addition, 

they should be educated regarding the importance of 

naps for bridging the gap between consolidated sleep 

episodes. Naps should be as long as possible and whenever 

feasible they should occur at the circadian times 

most conducive to natural sleep (i.e., early afternoon or 

early predawn hours according to the body clock). The 

principles outlined for good sleep hygiene should be 

followed to promote optimal nap quality and duration. 

Upon awakening from a nap lasting more than 40 min 

(i.e., where sleep inertia upon awakening is likely), there 

should be a wake-up period of at least 30 min prior to 

the performance of any safety-sensitive tasks. 

With regard to circadian adjustment techniques, it is our 

position that crewmembers who have moved to a new 



time zone or work schedule and who expect to remain in 

the new location or on the new schedule for several days 

should employ natural adjustment techniques such as controlling 

the timing of light exposure, meals, and other activities. 

The detailed recommendations presented earlier 

in this paper should be followed to the extent possible. 

Since aerobic exercise has been shown to improve the 

quality of a subsequent sleep period, it is our position 

that crewmembers engage in at least 30 min of aerobic 

exercise every 24 h. However, since exercise increases 

body temperature, most sleep experts say the best time 

to exercise is usually late afternoon. The exercise period 

should not be placed within 2 h immediately preceding 

bed time in order to allow the body to cool ( 76 , 199 , 235 ). 

Although evidence is weak that nutrition exerts a 

practically significant effect on sleep and alertness, we 

recommend that aircrews emphasize balanced meals at 

regular intervals to promote and maintain general 

health, and that they avoid consuming meals (particularly 

large meals) immediately prior to bedtime. It is 

possible that the ingestion of high-carbohydrate foods 

approximately 4 h prior to bedtime may promote sleep, 

but in general attempting to control sleep and alertness 

by manipulating dietary constituents is not advised. 

c. Non-FDA-Regulated Substances 

Alternative, non-FDA-regulated medicines and substances 

are sometimes used to counter fatigue through assisting 

with sleep or promoting alertness. Melatonin is 

probably the most used substance of the nonregulated 

ones available. Its efficacy as a hypnotic continues to be 

debated ( 211 , 237 ). Generally, as a sleep aid, it has not consistently 

been shown to be clinically efficacious for insomnia 

when taken during the biological night ( 32 ). However, 

there is evidence that melatonin has a soporific effect 

when taken outside the normal sleep period, particularly 

when taken to phase-advance the sleep period ( 8 ). 

Melatonin administration may help to overcome shift 

lag in operations involving rapid schedule changes and 

jet lag in circumstances requiring rapid time zone transitions. 

There is a substantial amount of research which 

indicates that appropriate administration of this hormone 

can improve circadian adjustment to new time 

schedules ( 9 , 32 , 206 ). There also is evidence that melatonin 

possesses weak hypnotic or “ soporific ” properties 

that may facilitate out-of-phase sleep ( 118 , 231 ). Typically, 

exogenous melatonin should be administered at 

approximately the desired bed time since melatonin naturally 

peaks after sleep onset. Melatonin is especially useful 

for facilitation of daytime sleep (early circadian sleep) 

but less efficacious for facilitation of normally timed 

nocturnal sleep unless one produces little or no melatonin. 

In normal individuals who are not stressed with circadian 

desynchrony [i.e., individuals who can safely be 

assumed to have a dim light melatonin onset (DLMO) in 

the range of ~2000 to 2200], melatonin should be ingested 

in the late afternoon (approximately 1700) to 

achieve a circadian phase advance, or in the morning 

(approximately 0800) to achieve a circadian phase delay 

( 34 ). For individuals who are suffering from circadian 

desynchrony, ingestion of melatonin or phototherapy 

should be used with proper guidance in order to avoid a 

circadian shift in the undesired direction. Since melatonin 

is not considered a drug, it is widely available for 

use with few restrictions, at least in the U.S. Unfortunately, 

most potential users of melatonin possess little 

knowledge about circadian rhythms and/or endogenous 

melatonin secretion, and this could lead to compromised 

alertness and decreased performance associated 

with improper use. 

Other substances to promote sleep are also available, 

but most of them have not been studied thoroughly and 

their effectiveness has not been established. However, of 

these substances, valerian and kava have the most research 

on efficacy. A systematic review of valerian concluded 

that, while some studies have found some evidence 

that valerian has significant effects on sleep, it is 

does not have the clinical efficacy needed to treat insomnia 

( 203 ). However, evidence suggests that valerian is a 

safe herb which can be helpful with mild insomnia when 

taken continuously. Good clinical studies are needed to 

establish both its efficacy for severe insomnia and its 

safety profile ( 95 , 136 , 230 ). Kava has been shown to help 

with sleep latency and sleep quality in people with insomnia, 

but more studies are needed to establish its efficacy 

and safety as well ( 136 ). 

For promoting alertness, caffeine can be considered a 

valuable non-FDA-regulated pharmacological fatigue 

countermeasure. Numerous studies have shown that 

caffeine increases vigilance and improves performance 

in sleep-deprived individuals, especially those who normally 

do not consume high doses ( 142 ). Caffeine (generally 

in the form of coffee, tea, or soft drinks) is already 

used as an alertness-enhancing substance in a variety of 

civilian and military flight operations, and it has proven 

safe and effective. For a very complete review of the applicability 

of caffeine in operations, see the Institute of 

Medicine report, especially pp. 79 – 82 ( 56 ). Caffeine is 

used best for the short-term elevation of cortical arousal; 

regular use may lead to tolerance and various undesirable 

side effects, including elevated blood pressure, 

stomach problems, and insomnia. Caffeine is widely 

available and affects the nervous system within 15 to 20 

min. The effects of caffeine last for about 4 to 5 h and 

may include a more rapid heartbeat and sharply increased 

alertness/decreased sleepiness; the effects may 

last up to 10 h in especially sensitive individuals. There 

are individual differences in the effects of caffeine on 

sleep. For some personnel, even small amounts can 

cause problems sleeping. For others, caffeine has no apparent 

detrimental effect on sleep. Chronic overuse may 

also cause dehydration, nervousness, and irritability. 

Tolerance to cortical arousal occurs with the repeated 

consumption of caffeine at more than about 200 to 300 

mg per day. Personnel should consume caffeine sparingly, 

and save the arousal effect until they really need 

it. This is called “ tactical caffeine use. ” The U.S. Armydeveloped 

caffeine gum, Stay Alert , is now in Army supply 

channels (NSN #8925-01-530-1219). It provides an 



excellent delivery mechanism for caffeine when the latter 

is needed during prolonged operations. The caffeine 

content of commonly used substances is listed in Table 

III . More specific guidance regarding caffeine use is provided 

in Section VI.c.i. 

The amino acid tyrosine, a precursor of the neurotransmitter 

norepinephrine, might be effective in 

countering the stress-related performance decrement 

and mood deterioration associated with sleep deprivation 

( 155 ). In a direct test of its effectiveness on cognitive 

performance during one night of total sleep loss, 

150 mg z kg 2 1 of tyrosine, administered in a split dose, 

resulted in an amelioration of the performance decline 

seen on a psychomotor task and a reduction in lapse 

probability on a vigilance task compared to placebo 

( 145 ). The results lasted approximately 3 h. While there 

are relatively few data, it appears that tyrosine is a relatively 

benign substance that may prove useful under 

high stress conditions, including those associated with 

sleep loss. 

Position Statement on Non-FDA-Regulated 

Substances 

While nonregulated substances are easy to purchase 

in many places in the U.S., they should still be consumed 

with the same caution as any prescription substance. In 

some individuals, many of the herbal remedies can lead 

to sleepiness levels which will impair performance. In 

addition, since these substances are not under federal 

control, the manufacturing quality is left to the individual 

companies. For example, one study found the stated 

amount of melatonin and the actual amount of melatonin 

varied considerably between lots as well as within 

bottles for several brands of melatonin sold over the 

counter ( 165 ). Research continues in determining the 

safety, dosage, formulation, and time of administration 

of melatonin since this substance shows the most promise 

in helping sleep and circadian disorders. However, 

there is still debate about its use and long-term safety, 

and for this reason we do not recommend the use of 

melatonin to readjust circadian rhythms or to promote 

sleep. Other substances such as valerian and kava also 

should not be relied upon to manipulate either sleep or 

performance. Caffeine, on the other hand, is an effective 

alertness-enhancing compound, and it is our position 

TABLE III. CAFFEINE CONTENT OF COMMON DRINKS AND 

OVER-THE-COUNTER MEDICINES. 

Substance 

Average Caffeine Content 

1 cup Maxwell House w 100 mg 

1 Starbucks w Short 250 mg 

1 Starbucks w Tall 375 mg 

1 Starbucks w Grande 550 mg 

1 Coke w 50 mg 

1 Mountain Dew w 55 mg 

1 cup tea 50 mg 

2 Anacin w 65 mg 

2 Excedrin Xtra. Strength 130 mg 

1 Max. Strength NoDoz w 200 mg 

that it should continue to be used as an aviation fatigue 

countermeasure. Crewmembers should adhere to the 

following : 1) avoid ingesting more than 1000 mg of caffeine 

in any 24-h period; 2) make an effort to use caffeine 

judiciously (i.e., only when it is truly needed to reduce 

the impact of fatigue); and 3) avoid ingesting caffeine 

within 4 h of bedtime. However, the effects of caffeine 

on sleep are dependent on factors such as usual caffeine 

consumption and age ( 199 ). Here are some situations 

where using caffeine makes sense: 1) leading in to the 

predawn hours; 2) midafternoon when the alertness dip 

is greater because of inadequate nocturnal sleep; and 3) 

prior to driving after night duty, but not within 4 h of 

going to sleep. 

V. NEW TECHNOLOGIES 

The need for real-time fatigue detection technologies 

and predictive modeling algorithms that focus on minimizing 

fatigue-related errors, incidents, and accidents 

during flight has been realized for several years. This is 

largely due to fatigue’s continued persistence as an occupational 

hazard and the related cognitive deficits that 

inhibit the ability of an operator to identify decreases in 

alertness ( 31 ). Therefore, many efforts have focused on 

developing unobtrusive technologies that aim to detect 

fatigue in pilots prior to its onset so that an operationally 

valid and effective countermeasure can be implemented. 

Advances in fatigue technologies and algorithm 

development have made this goal achievable. However, 

before being transitioned to operational environments, 

these technologies and algorithms must be shown to 

meet a number of engineering, scientific, practical, and 

legal/ethical standards and criteria ( 69 ). Efforts to demonstrate 

validity have been conducted through a variety 

of venues including controlled laboratory settings, simulation 

research protocols, operational evaluations, and 

workshops involving subject matter experts from the 

field ( 68 , 70 , 72 , 100 , 125 , 212 ). 

a. On-Line, Real-Time Assessment 

On-line operator status technologies are the most 

common of the fatigue monitoring devices because of 

their ability to provide meaningful measures of alertness 

levels and performance ability in real time ( 69 ). 

They aim to monitor some aspect of the individual’s 

physiology or behavior that is sensitive to increasing 

fatigue and sleepiness levels. Available and developing 

on-line, operator status detection technologies monitor 

either the physiological behavior of the individual 

(EEG, eye gaze, facial feature recognition) or their 

physical characteristics (muscle tone, head position, 

percent eye closure, wrist inactivity). They offer great 

potential for pilots who are challenged with maintaining 

alertness and performance during long, uneventful 

flights ( 36 ). 

Research over the past 40 yr has established the EEG 

as a highly predictive and reliable neural index of cognition 

along with event-related brain potentials (ERPs) 

( 82 ). It has been accepted as the ‘” gold standard ” for the 



detection of impaired alertness. These EEG signals and 

analyses are now being incorporated into a real-time 

technological countermeasure device for fatigue detection 

( 109 ). For example, the B-alert w ( 20 ) has been validated 

as an alertness indicator for driver fatigue ( 115 ) 

and has also demonstrated sensitivity to individual 

fatigue vulnerability ( 116 ). The B-alert w system can also 

be implemented in combination with ERPs to capture a 

more detailed image of information processing in the 

brain ( 20 ). Other researchers (e.g., 120 ) are also developing 

EEG-based drowsiness estimation systems based on 

computed correlations between changes in EEG power 

spectrum and fluctuations in driving performance. From 

this information, individualized linear regression models 

for each subject applied to principal components of 

EEG spectra can be constructed for further real-time 

monitoring. 

Although the detection of fatigue based on the EEG 

changes that occur simultaneously in the delta, theta, 

alpha, and beta bands has been accepted as a valid 

measure of fatigue, obtaining brain wave activity in 

the operational environment is often times not feasible. 

Research has shown that the eye and visual system, 

under central nervous system control, can also provide 

information about an individual’s alertness level and 

cognitive state ( 39 , 121 , 112 , 207 ). Deteriorations in many 

ocular measures occur with fatigue and extended waking 

periods, with the most sensitive being those that 

change just prior to the sleep onset period, such as eye 

blinks, long duration eye closures, eye movements, 

and pupillary response. Various devices have been designed 

to monitor these ocular changes, but each device 

differs somewhat in terms of exactly what is measured, 

how it is measured, and how the data are 

processed. In addition, there are differences in the precise 

nature of the fatigue-monitoring algorithms and in 

the hardware technology used to obtain the ocular 

measures. Some are unobtrusive and require simple 

video while others can require the user to place a sensor 

near the eye or require the person to wear specially 

equipped eyeglasses. A number of promising ocular 

devices are in the validation phase for real-time, noninvasive 

detection of operator fatigue. These include 

devices that assess the percentage of eye closure, such 

as the Co-Pilot (Attention Technologies, PA), Optalert 

(Sleep Diagnostics, Australia), and Eye-Com (Eye-Com 

Corp., Reno, NV). Selection of the PERCLOS metric (a 

measure of the proportion of time subjects had slow 

eye closures; 228 , 229 ) for these devices is based on research 

demonstrating its high correlation with psychomotor 

vigilance behavior ( 70 ). 

Facial feature recognition technology is also currently 

being validated as a fatigue detection device ( 73 , 94 ; 

Dinges DF. Personal communication; 2008). The simultaneous 

extraction of changes in multiple locations on 

the face such as around the eyes, nose, and mouth provide 

a great deal of information regarding individual 

alertness levels. Moreover, Ji, Zhu, and Lan ( 102 ) have 

incorporated other critical factors such as PERCLOS and 

circadian variations into facial feature recognition technology 

for the development of a real-time, nonintrusive 

monitor device for fatigue. 

Additional fatigue detection devices that compared 

successfully to the EEG technique and/or the PERCLOS 

technique include a wrist-worn alertness device that 

triggers an alarm sound when wrist inactivity occurs for 

a preset amount of time (e.g., 5 min; 233 ) and a device 

that assesses head position “ XYZ ” data analyzed over 

various time periods to signify micronods or microsleeps 

( 104 ). 

All fatigue detection devices, independent of the variable 

being measured, have both positive and negative 

aspects. Their usefulness as real-time technologies is dependent 

on the requirements and conditions of the operational 

environment and some may not even be practical 

for use in highly restrictive environments such as the 

flight deck. For example, based on a study that showed 

an automated PERCLOS device was effective in improving 

alertness and performance in truck drivers ( 125 ), a 

similar study was conducted in a B747-400 flight simulator 

( 127 ). The goal of the study was to establish the feasibility, 

potential usefulness, and applicability of the automated 

PERCLOS monitor for drowsiness detection and 

mitigation of fatigue on the flight deck. The automated 

PERCLOS system with feedback did not significantly 

counteract decrements in performance, physiological 

sleepiness, or mood on the flight deck, which was very 

different from the results found in the truck-driving environment. 

This was largely due to the PERCLOS system 

having a limited field of view that could not capture 

pilots ’ eyes at all times during the flight due to operational 

requirements of constant visual scanning and 

head movements. These results clearly demonstrate 

that, although an automated, real-time technology may 

be valid in one operational environment, it does not always 

transition to another operational environment 

without the emergence of implementation obstacles. 

b. Off-Line Fatigue Prediction Algorithms 

Off-line fatigue prediction algorithms are being developed 

to provide an estimate of an individuals ’ alertness 

level or performance effectiveness during a work 

period to be performed in the future. These measures 

(e.g., alertness levels, performance estimates) of physiological 

state are measured relative to a standard such as 

the individual’s baseline and/or a group norm ( 91 ). For 

example, ocular-based, readiness-to-perform, or fitnessfor-duty 

devices often measure various aspects of the 

visual system of the individual prior to a duty period to 

determine if they can maintain optimal performance 

throughout the work period ( 60 ). Such a device as the 

FIT device ( 161 ) has already been shown to detect 

changes attributable to sleep loss ( 182 – 184 ). 

Over the years, there have also been recent developments 

of biomathematical models of alertness for the 

prediction of alertness and performance levels ( 125 ). 

They can be very useful in the prediction of performance 

or effectiveness levels when comparing different operational 

schedules. Although models can differ in their 



specific algorithm, they all aim to model the interaction 

of sleep and circadian processes and effects on the sleep/ 

wake cycle and waking neurobehavioral performance. 

The operational usefulness of these models lies directly 

in them being incorporated into scheduling tools. Such 

tools can be used to develop work schedules that maximize 

safety by: 1) predicting times when performance is 

optimal; 2) identifying timeframes in which recovery 

sleep will be most restorative; and 3) determining what 

impact proposed work/rest schedules will have on 

overall neurobehavioral functioning ( 126 ). 

Models of alertness and performance vary in their specific 

algorithms and differ in the number and type of input 

variables, output variables, and goals and capabilities. 

It is also important to consider the operational 

environment for their intended use. Of the seven models 

evaluated at a modeling workshop sponsored by the U.S. 

Department of Defense, U.S. Department of Transportation, 

and NASA, only two of them specifically relied on 

aviation data for development or stated their relevance 

to aviation operations ( 126 ). At the time of the workshop 

in 2002, the System for Aircrew Fatigue Evaluation 

(SAFE) model was specifically developed for aviation 

operations. It had been adjusted using data collected on 

long-haul flights and required aviation-specific variables 

for its input ( 19 ). Another model, the Sleep, Activity and 

Fatigue Task Effectiveness (SAFTE) model was developed 

for military and industrial settings and included a 

translation function for pilots. The SAFTE model is the 

foundation of the Fatigue Avoidance Scheduling Tool 

(FAST), which was designed to help optimize the operational 

management of aviation ground- and flightcrews 

( 101 ). While all of the biomathematical modeling software 

showed promise in the prediction of performance, 

there is room to improve their validity and reliability 

based on refinements with real world data, and they 

should not be transitioned to operational environments 

until their scientific validity can be demonstrated ( 66 ). 

Position Statement on New Technologies 

Fatigue detection technologies (fitness for duty and 

real-time assessment devices) and scheduling tools that 

incorporate biomathematical models of alertness should 

not be solely relied upon for the determination of safe or 

‘ fatigue-free ’ flights. They are tools that can be effectively 

incorporated as part of an overall safety management 

approach and should not be used in place of regulatory 

limitations. Selection of the ‘ best tool ’ should be 

dependent on its demonstrated validity for mitigating fatigue 

risk during aviation operations . 

At present, none of the real-time fatigue detection 

technologies have been sufficiently proven in an aviation 

environment (with the possible exception of the 

wrist-worn alertness device that triggers an alarm sound 

when wrist inactivity occurs for a preset amount of time) 

to warrant widespread implementation. However, some 

crew scheduling approaches based on validated fatigueprediction 

models have already been proven, to a limited 

extent, feasible and worthwhile. The SAFTE model 

for instance, is currently being used in a number of aviation 

settings to evaluate the fatiguing impact of different 

schedules and to help design better alternatives. 

Refinement of both the new fatigue monitoring technologies 

and scientifically based scheduling software 

must continue, and once they are validated for specific 

types of operations, they should be incorporated as part 

of an overall safety management approach supplementing 

regulatory duty limitations. Fatigue detection technologies 

and biomathematical models can also be used 

in combination. The online, realtime measurements (e. 

g., actigraphy, performance measures) could be used as 

input data to the scheduling tools, thus increasing their 

predictive value, being reflective of what is occurring 

during actual operations. Research is also needed to 

identify embedded (flying) performance metrics that 

are sensitive to fatigue over time, allowing for model refinement 

and continuous assessment of the safety of 

operations. 

A final consideration in the development of new technologies 

is to combine biomathematical models of alertness 

with scheduling tools that do not have a foundation 

in sleep and circadian research (e.g., tools that 

incorporate labor contract rules, government regulations, 

available staff, vacation time, currency training, 

etc.). Combining the two would result in scheduling regimes 

that consider both the physiological limitations of 

humans and operational constraints, resulting in both 

compliant and safe operations. 

VI. MILITARY AVIATION 

a. Relevant Regulations and Policies 

A review of the fatigue management (crew rest) policies 

implemented by the U.S. Army, the U.S. Air Force, 

and the U.S. Navy shows far less complexity than is 

found in the civil aviation regulations. Complete guidance 

may be found in Army Regulation 385-95 (10 Jan 

2000), Air Force Instruction 11-202 v3 (05 Apr 2006), and 

OPNAV Instruction 3710.7T (01 Mar 04). 

b. Crew Rest and Duty Limitations 

The primary requirement for crew rest and duty limitations 

is somewhat similar to that specified in the civil 

aviation regulations; specifically, that 8 h of continuous 

rest be obtained prior to the duty period. The U.S. Air 

Force instruction requires a 12-h nonduty crew rest period 

in which 8 h of uninterrupted sleep must be obtained 

in the 12 h prior to duty. If this 8-h sleep period is 

interrupted, another 8 h must be added. The U.S. Navy 

instruction requires that 8 h of continuous rest be 

obtained within the 24-h period, and that any continuous 

wakefulness period should not exceed 18 h. If the 

18-h requirement is not met, a minimum of 15 h of continuous 

off-duty time must follow. The U.S. Army at one 

time had one of the most detailed crew rest and duty 

limitation guides of the three U.S. services. However, 

the Army guidance now more generally states that commanders 

are responsible for endurance management by 

ensuring that fatigue is controlled or eliminated as a risk 



factor in all operations by providing for sufficient sleep 

time in each 24-h period as well as for circadian adjustment 

of the individual body clocks of personnel changing 

time zones or work cycles. Army commanders are 

directed to consult the Leaders Guide to Crew Endurance 

Management ( 57 ) for complete details. 

Air Force Instruction 11-202, Vol. 3, offers some of the 

most detailed current guidance. It advises commanders 

and mission planners to consider fatigue-related factors 

for upcoming flight missions including the fatiguing impact 

of adverse weather, temperature extremes, night 

operations, and mission delays, as well as the fatigue 

from sleep loss and continuous work. Additional guidance, 

paraphrased from Air Force Instruction 11-202 

(waivers may be requested for specific circumstances) 

and the U.S. Navy guidance paraphrased from Chief of 

Naval Operations Instruction 3710.7T, are listed below: 

U.S. Air Force Guidance for Scheduling Flight Missions to Avoid 

Fatigue in Aircrew: 

• Provisions should be made for augmenting flightcrews when 

possible to permit in-flight rest periods. 

• Cockpit naps (taken by one crewmember at a time) of up to 45 

min in duration are authorized during noncritical flight phases, 

and multiple naps are permitted when feasible. 

• Crew bunks or other suitable rest facilities should be provided 

on board aircraft when possible. 

• Adequate crew rest is required prior to flight duty periods. 

Normally, this means 12 h off duty every 24 h. There should be 

a minimum of 10 h of restful time that includes an opportunity 

for at least 8 h of uninterrupted sleep during the 12 h preceding 

the flight duty period. 

• Shorter off-duty periods of 10 h may be used as an exception in 

continuous operations, but this exception should be minimized, 

and after several days of shorter off-duty periods, commanders 

should provide sufficient rest to counter cumulative fatigue. 

• Maximum flying time should be limited to 56 h per 7 d, 125 h 

per 30 d, and 330 h per 90 consecutive days. 

• If nonflight duties significantly extend the overall duty period 

(by 2 h or more), consideration should be given to reducing the 

number of allowed flight hours. 

• Generally speaking, the maximum flight duty period for any 

given day should fall within the range of 12 to16 h in situations 

where crew augmentation is not possible. 

• When augmented crews are an option, duty days normally can 

extend to 16 to 24 h (in the case of the B-2 Bomber, some missions 

extend to 44 h). 

• Factors affecting maximum flight duty period include: single vs. 

multiseat aircraft, level of automation, availability of onboard 

rest facilities, and type of flight mission. 

• Alertness management strategies such as techniques to promote 

preduty sleep, extended crew rest periods, controlled 

cockpit rest, bright light exposure, activity breaks, pharmacological 

sleep and alertness aids, and fatigue management education 

should be implemented as appropriate. 

U.S. Navy Guidance for Scheduling Flight Missions to Avoid 

Fatigue in Aircrew: 

• Schedule ground time between flight operations to allow flightcrew 

to eat and obtain at least 8 h of uninterrupted sleep. 

• Flightcrew should not be scheduled for continuous alert or 

flight duty in excess of 18 h. If mission requirements exceed 18 

h, then 15 h of continuous off-duty time should be provided. 

• Following a time zone change of at least 3 h, flightcrew requires 

close observation by the flight surgeon since performance 

will be compromised during the adjustment period. 

• For single-piloted aircraft: Daily flight time should not exceed 3 

flights or 6.5 h total flight time for flight personnel. The weekly 

maximum flight time should not normally exceed 30 h, 65 h 

per 30 d, 165 h per 90 d, and 595 h per 365 d. 

• For multipiloted aircraft: Individual daily flight time should not 

exceed 12 h for flight personnel. The weekly maximum flight 

time for ejection seat aircraft should not normally exceed 50 h, 

80 h per 30 d (100 and 120 for nonpressurized and pressurized 

aircraft, respectively), 200 h per 90 d (265 and 320 for nonpressurized 

and pressurized aircraft, respectively), and 720 h per 

365 d (960 and 1120 for nonpressurized and pressurized aircraft, 

respectively). These limitations assume an average requirement 

of 4 h of ground time for briefing and debriefing. 

• If operational tempo requires the flight time limitations to be 

exceeded, the commanding officer, with the flight surgeon’s 

advice, will closely monitor and specifically clear flight personnel, 

commenting particularly in regard to stress level and adequacy 

of rest and nutrition. 

• Particular notice should be made of flights involving contour, 

nap of the Earth, chemical defense gear, night and night vision 

devices, and adverse environmental factors (i.e., dust, cloud 

cover, precipitation) since these flights are more stressful and 

demanding than daytime VFR conditions. 

c. Stimulants/Wake Promoters 

As noted above, alertness-enhancing medications are 

one option for sustaining the wakefulness of flightcrews 

during extended missions in which adequate crew rest 

is not possible. Needless to say, these compounds should 

not be considered a replacement for adequate crew rest 

planning and they should never be considered a substitute 

for restorative sleep. However, in sustained aviation 

operations, the occasional use of the alertnessenhancing 

medications such as dextroamphetamine 

(authorized by all three U.S. services) and modafinil 

(authorized for use in the U.S. Air Force) can often significantly 

enhance the safety and effectiveness of sleepdeprived 

personnel. 

Modafinil (Provigil w , Vigilw , Alertecw and others): The 

prescription drug modafinil (100 to 200 mg) exerts a wide 

array of positive effects on alertness and performance. 

Lagarde and Batejat ( 108 ) found that 200-mg 

doses every 8 h reduced episodes of microsleeps and 

maintained more normal (i.e., rested) mental states and 

performance levels than placebo for 44 h of continuous 

wakefulness (but not the full 60 h of sleep deprivation). 

Wesensten et al. ( 226 ) found 200 to 400 mg doses of 

modafinil effectively countered performance and alertness 

decrements in volunteers kept awake for over 48 h. 

Caldwell and colleagues ( 47 ) found that 200 mg of 

modafinil every 4 h maintained the simulator flight performance 

of pilots at near-well-rested levels despite 40 h 

of continuous wakefulness, but that there were complaints 

of nausea and vertigo (likely due to the high dosage 

used). A more recent study with U.S. Air Force F-117 

pilots indicated that three 100-mg doses of modafinil (administered 

every 5 h) sustained flight performance within 

27% of baseline levels during the latter part of a 37-h period 

of continuous wakefulness. Performance under the 

no-treatment condition was degraded by over 82% ( 46 ). 

Similar beneficial effects were seen on measures of alertness 

and cognitive performance. Furthermore, the lower 

dose produced these positive effects without causing the 

side effects noted in the earlier study ( 47 ). Due to these 

and other positive results, modafinil is gaining popularity 

as a way to enhance the alertness of sleepy personnel, 

largely because it is considered safer and less addictive 

than compounds such as the amphetamines. Modafinil 

also produces less cardiovascular stimulation than 



amphetamine, and despite its half-life of approximately 

12 to 15 h ( 159 , 169 ), the drug’s impact on sleep architecture 

is minimal. However, it should be kept in mind that 

modafinil has not been as thoroughly tested as dextroamphetamine 

in real-world operational environments 

and some data suggests that modafinil is less effective 

than amphetamine ( 132 ). Nevertheless, approval has 

been received for the use of modafinil in certain longrange 

U.S. Air Force combat aviation missions, and it is 

likely that modafinil soon will be approved for use in the 

U.S. Army and the U.S. Navy. 

Amphetamine (Dexedrine w , Dextrostatw ): Dextroamphetamine 

(5 to 10 mg) has been authorized for use by all 

three U.S. services for certain types of lengthy (i.e., 12 or 

more hours) flight missions. In comparison to caffeine, 

dextroamphetamine appears to offer a more consistent 

and prolonged alerting effect ( 223 ). In comparison to 

modafinil, studies suggest that amphetamine is either 

more efficacious ( 132 ) or, at least in the case of 40-h sleepdeprivation 

periods, equivalent ( 41 ,160 ,225 ). In terms of 

the efficacy of amphetamine as a fatigue countermeasure, 

Newhouse et al. ( 148 ) studied d-amphetamine 

(5, 10, or 20 mg) in people deprived of sleep for over 48 

h and found that 20 mg d-amphetamine (administered 

after 41 h of continuous wakefulness) produced marked 

improvements in addition/subtraction (lasting for over 

10 h), a gradual improvement in logical reasoning 

(significant between 5.5 and 7.5 h postdose), a longlasting 

improvement in the speed of responding during 

the choice reaction-time task (10 h), and an increase in 

alertness for 7 h. It was noted that the drug did not impair 

judgment. The 10-mg dose exerted fewer and 

shorter-lasting effects, whereas the 5-mg dose was ineffective. 

Two flight simulation studies involving U.S. 

Army pilots indicated that repeated 10-mg doses of dextroamphetamine 

(given at midnight, 0400, and 0800) 

maintained flight performance and alertness nearly at 

well-rested levels throughout 40 h of continuous wakefulness 

( 44 , 45 ). Benefits were especially noticeable between 

0300 and 1100, when fatigue-related problems 

were most severe. In a later study, 10 pilots completed a 

series of 1-h sorties in a specially instrumented UH-60 

helicopter during 40 h of sleep deprivation. The results 

revealed that 10-mg doses of dextroamphetamine sustained 

performance nearly as well under actual in-flight 

conditions as in the laboratory ( 42 ). A follow-on simulator 

investigation extended these findings by showing 

that with additional amphetamine dosing, pilot performance 

and alertness could be sustained for over 58 continuous 

hours of wakefulness (2 nights of sleep loss) 

( 50 ). Reports from the field indicate dextroamphetamine 

has been used successfully in a number of combat situations 

such as Vietnam ( 58 ), the 1986 Air Force strike on 

Libya ( 192 ), and Operation Desert Shield/Storm ( 59 ). 

Emonson and Vanderbeek ( 81 ) found that U.S. Air Force 

pilots who were administered dextroamphetamine during 

Operation Desert Shield/Storm were better able to 

maintain acceptable performance during continuous 

and sustained missions, and that the medication contributed 

to both safety and effectiveness. To date, no major 

side effects or other problems have been reported 

from the medical use of dextroamphetamine in military 

settings. In light of these and other findings, dextroamphetamine 

doses of 10 to 20 mg (not to exceed 60 mg per 

day) are recommended for situations in which heavily 

fatigued military pilots simply must complete the mission 

despite dangerous levels of sleep deprivation. 

Guidance from the U.S. Air Force is shown below. 

U.S. Air Force Combat Aviation Operations Guidance for Use of 

Stimulants: 

• Prior to the operational use of dextroamphetamine or 

modafinil, an informed consent agreement must be obtained 

to ensure that crews are fully aware of both the positive and 

the potential negative effects of these compounds. 

• The decision to authorize the use of alertness-enhancing 

compounds should be made by the Wing Commander in conjunction 

with the Senior Flight Surgeon. 

• All distribution of alertness-enhancing medications must be 

closely monitored and documented. 

• Ground testing (during nonflight periods) is required prior to 

operational use. 

• The currently authorized dose of dextroamphetamine is 5 to 

10 mg, and although the dosing interval is not explicitly 

stated, a 4-h interval is often recommended. No more than 60 

mg should be administered in any 24-h period, and often, no 

more than 30 mg are administered. 

• The currently authorized dose of modafinil is 200 mg every 8 

h, not to exceed 400 mg in any 24-h period; however, recent 

F-117 research has indicated that 100-mg doses also are efficacious 

(and this lower dose is authorized as well). 

• The use of alertness-enhancing compounds normally can be 

authorized in fighter missions longer than 8 h or bomber missions 

longer than 12 h (although exceptions can be made). 

• Caffeine generally is not considered to be a suitable alternative 

for modafinil or dextroamphetamine; however, caffeine 

in the form of foods or beverages may be consumed without 

restriction. Caffeine in the form of tablets or capsules can only 

be used after flight surgeon approval. 

The U.S. Army and U.S. Navy guidance is mostly consistent 

with U.S. Air Force guidance with the most notable 

exception being that modafinil is not currently authorized 

in the Army or Navy. The U.S. Army guidance for 

use of dextroamphetamine endorses the administration 

of 5- to 10-mg doses and specifies that no more than 30 

mg may be used in any 24-h period. It is also stated that 

the medication not be used to sustain wakefulness longer 

than 64 continuous hours. The U.S. Navy guidance suggests 

that dextroamphetamine be administered in 5-mg 

doses which may be repeated every 2 to 3 h; however, total 

dosage should not exceed 30 mg in any 24-h period. 

An upper level for the duration of any period of continuous 

wakefulness is not specified, but it is clear that extended 

periods without sleep should be avoided. 

Position Statement on the Use of Stimulants to 

Sustain Flight Performance 

Alertness-enhancing compounds of some description 

are already authorized for use in all U.S. military 

services during periods of unavoidable sleep deprivation. 

Thus far, the U.S. Air Force is the only service that 

has authorized the use of both modafinil and dextroamphetamine, 

whereas only dextroamphetamine is 

currently authorized by the U.S. Army and U.S. Navy. 

Based on Air Force experience, it is recommended that 



modafinil use be sanctioned by all three U.S. services 

under guidance consistent with that currently followed 

by the Air Force. Relatively uncontrolled caffeine 

use is also an option in all three U.S. services, 

and the use of caffeine, while not recommended as a 

primary pharmacological fatigue countermeasure, 

should continue to be sanctioned by the U.S. services. 

Aircrew should avoid habituation to caffeine and take 

advantage of the cortical stimulant properties of caffeine 

when it is needed to help ensure safe operations. 

More specifically, when aircrews are not suffering from 

the effects of fatigue, they should limit their total daily 

caffeine consumption from all sources to 200 to 250 mg 

per day . Additional doses of caffeine should be used 

during situations in which fatigue elevates the risk of 

a mishap. These situations may include low-workload, 

long-duration transits over land or water during the 

predawn hours; approach and landing during the predawn 

hours; and approach and landing at the end of 

an extraordinarily long crew duty day. In any given 

24-h period, the total amount of caffeine consumed 

should not exceed 1000 mg. Aircrew should be aware 

of the 4-6-h half-life of circulating caffeine and preplan 

its use such that postduty day sleep is disturbed minimally 

by caffeine use. 

With the exception of caffeine and various nutritional 

supplements, no alertness-enhancing medications are 

currently authorized for use in any type of civil aviation 

operation. Due to the fact that civil operations generally 

are more predictable than military operations, and due 

to the fact that prolonged periods of sleep deprivation 

are not the norm in civil operations (whereas such periods 

are often unavoidable in the military sector), it 

would seem prudent to withhold widespread authorization 

of prescription alertness enhancers in the civilian 

aviation sector. Also, there is the matter that intense military 

operations are generally time limited, exposing 

military pilots to only relatively brief periods in which 

intense sleep deprivation necessitates the administration 

of appropriate counter-fatigue medications, whereas 

civil operations continue day in and day out for the duration 

of a pilot’s career, potentially exposing moderately 

fatigued pilots to years of chronic medication use if 

such medications were authorized. This difference between 

military and civil aviation scenarios likewise 

seems to argue against the widespread authorization of 

alertness-enhancing drugs in civil operations. However, 

it would be worthwhile to consider the temporary authorization 

of counter-fatigue medications in civil emergency 

flight operations such as when airlifting disaster 

relief supplies, rapidly evacuating medical casualties 

following some catastrophic event, etc. 

d. Sleep-Inducing Agents 

When individuals are given the opportunity to sleep, 

but are unable to do so due to various circumstances 

(i.e., wrong circadian time, poor sleep conditions), sleep 

aids represent a viable countermeasure. The characteristics 

of various hypnotics were discussed earlier. However, 

each branch of the military has its own policy concerning 

the use of hypnotics. Table IV indicates the U.S. military’s 

policies on hypnotic use. As with the stimulant 

policy, a ground test is necessary prior to use during operations. 

The U.S. Navy guidance explicitly forbids the 

administration of more than one dose of a hypnotic per 

24-h period, with no more than 2 d of consecutive use of 

temazepam. There is also guidance for planning and 

briefing in the grounding restriction ( 210 ). As with other 

medications, the use of hypnotics is voluntary. 

Position Statement on the Military Use of 

Sleep-Inducing Agents 

Sleep-promoting compounds are useful for mitigating 

the sleep loss associated with circadian disruptions, 

poor sleeping conditions, and poor sleep timing often 

associated with combat or other high-tempo military 

operations. They should continue to be authorized in circumstances 

where: 1) their use is justified by the presence 

of one or more of the previously noted factors; 2) there is 

appropriate medical supervision; 3) there is evidence 

that the crewmember has completed a pre- mission 

TABLE IV. U.S. MILITARY POLICIES FOR HYPNOTIC USE. 

Medication Dose Half-life Grounding 

U.S. Army Rest Agent Policy 

Temazepam (Restoril w ) 15 or 30 mg 8.0 – 12.0 h 24 h 

Triazolam (Halcion w ) 0.125 or 0.25 mg 2.0 – 4.0 h 9 h 

Zolpidem (Ambien w ) 5 or 10 mg 2.0 – 2.5 h 8 h 

Zaleplon (Sonata w ) 5 or 10 mg 1.0 h 8 h 

U.S. Air Force No-Go Pill Policy 

Temazepam (Restoril w ) 15 or 30 mg 8.0 – 12.0 h 12 h 

Triazolam (Halcion w ) Not authorized na na 

Zolpidem (Ambien w ) 10 mg 2.0 – 2.5 h 6 h 

Zaleplon (Sonata w ) 10 mg 1.0 h 4 h 

U.S. Navy Sleep Initiator Policy 

Temazepam (Restoril w ) 15 mg 8.0 – 12.0 h 7 h 

Triazolam (Halcion w ) Not authorized na na 

Zolpidem (Ambien w ) 5 or 10 mg 2.0 – 2.5 h 6 h 

Zaleplon (Sonata w ) Not authorized Na na 



ground-test to check for idiosyncratic reactions; and 4) 

the mission is such that there is little or no chance that 

the aircrew member will be subject to an unexpected 

truncation of the sleep period. Obviously, personnel 

who are “ on-call ” and may need to fly a mission at a 

moment’s notice should not utilize sleep medications of 

any type due to the possibility that the medication 

would not have time to be adequately metabolized prior 

to returning to duty. Education concerning use and effects, 

ground testing, and grounding times are important 

for successful and safe use of sleep substances. 

e. Nonpharmacological Countermeasures and Strategies 

Of the U.S. military services, the Air Force guidance 

on nonpharmacological counter-fatigue strategies is the 

most specific. For instance, controlled cockpit rest is explained 

in detail below: 

Cockpit Rest Guidelines: 

• Controlled cockpit rest may be implemented when the basic 

aircrew includes a second qualified pilot. 

• Cockpit rest must be restricted to noncritical phases of flight 

between cruise and 1 h prior to planned descent. 

• Resting crewmember must be immediately awakened if a situation 

develops that may affect flight safety. 

• Cockpit rest shall only be taken by one crewmember at a time. 

• All cockpit crewmembers including the resting member must 

remain at their stations. 

• A rest period shall be limited to a maximum of 45 min. 

• More than one rest period per crewmember is permitted if the 

opportunity exists. 

• Controlled cockpit rest is not authorized with any aircraft system 

malfunctions that increase cockpit workload. 

• Cockpit rest should not be used as a substitute for any required 

crew rest. 

Of course, the U.S. Air Force as well as the U.S. Army 

and the U.S. Navy brief personnel on the correct use of a 

variety of alertness-management strategies such as the 

promotion of preduty sleep, implementation of extended 

crew rest periods when possible, bright light exposure 

when feasible, in-flight activity/rest breaks, and 

general fatigue management. All can be used in combination 

when appropriate. 

VII. CONCLUSIONS AND RECOMMENDATIONS 

Given the state of the art in fatigue countermeasures, 

our summary recommendations, most of which apply 

to both civil and military aviation except where noted, 

are as follows: 

Education — about the dangers of fatigue, the causes 

of sleepiness, and the importance of sleep and proper 

sleep habits — is one of the keys to addressing fatigue 

in operational contexts. All aviation personnel including 

supervisors, schedulers, and crewmembers should 

be educated regarding the effects of fatigue, the factors 

responsible for fatigue, and the available scientifically 

proven fatigue countermeasures. Ultimately, the 

individual pilot, schedulers, and management must 

be convinced that sleep and circadian rhythms are important 

and that quality day-to-day sleep is the best 

possible protection against on-the-job fatigue. Recent 

studies have made it clear that as little as 1 to 2 h of 

sleep restriction almost immediately degrades vigilance 

and performance in subsequent duty periods 

( 17 , 214 ). Thus, educational programs should communicate 

the central points conveyed in this position 

paper: 

1) fatigue is a physiological problem that cannot be overcome by 

motivation, training, or willpower; 

2) people cannot reliably self-judge their own level of fatigue-related 

impairment; 

3) there are wide individual differences in fatigue susceptibility that 

must be taken into account but which presently cannot be reliably 

predicted; 

4) there is no one-size-fits-all “ magic bullet ” (other than adequate 

sleep) that can counter fatigue for every person in every situation; 

but 

5) there are valid counter-fatigue strategies that will enhance safety 

and productivity, but only when they are correctly applied. 

Concurrent with the educational effort, a large-scale 

program should be undertaken to implement a nonprescriptive 

fatigue risk management system (FRMS) that 

determines optimum flight schedules from both a physiological 

and operational standpoint on a case-by-case 

basis since prescriptive hours-of-service limitations cannot 

account for human circadian rhythms or sleep propensity. 

With regard to in-flight counter-fatigue strategies, 

we concur with the present primary reliance on 

in-flight bunk rest in long-haul operations, but suggest 

that computerized scheduling tools be used to optimize 

crew rostering and bunk rest timing. We likewise believe 

that short in-flight breaks are beneficial, and we recommend 

that any regulations governing the use of these 

breaks be liberalized (i.e., that alertness-promoting 

breaks be permitted as a clearly acceptable reason for 

pilots to deviate from the requirement to remain in their 

seats with seatbelts fastened at all times). Given the scientific 

evidence that cockpit napping is safe and highly 

effective, as well as clear indications that the general 

public appreciates the value of cockpit napping, we take 

exception to the current prohibition on in-seat cockpit 

napping in civil aviation, and instead recommend that 

in-seat cockpit naps up to 45 min in duration be permitted 

in U.S. commercial flight operations as long as the 

naps are not used as a replacement for other sleep opportunities 

(i.e., bunk sleep or pre/post duty sleep). This 

procedure is in agreement with current U.S. Air Force 

policy. 

To promote on-duty alertness in the absence of sufficient 

contiguous hours of preduty sleep, the importance 

of napping should be emphasized as a primary strategy. 

Off-duty naps should be as long as possible and whenever 

feasible they should occur at the circadian times 

most conducive to natural sleep (i.e., early afternoon or 

early predawn hours according to the body clock). The 

principles outlined for good sleep hygiene should be 

followed to promote optimal nap quality and duration. 

Upon awakening from a nap, there should be a wakeup 

period of at least 30 min prior to the performance of 

any safety sensitive tasks. When naps are insufficient, 

personnel should consider the ingestion of caffeine (up 

to 1000 mg per day) as an alertness-enhancing strategy, 

and they should make an effort to use caffeine judi- 



ciously (i.e., only when it is truly needed to reduce the 

impact of fatigue). 

With regard to the use of pharmacological compounds 

in civil flight operations, it is our position that on the one 

hand, prescription alertness-enhancing compounds not 

be authorized on a routine basis since they are not justified 

by a cost/benefit analysis for flight operations that 

are relatively predictable, and there is insufficient medical 

oversight to ensure appropriate use. Also, it should 

be noted that when civil as opposed to military flights 

are cancelled or modified due to crew fatigue, there is 

virtually no “ downside ” from a safety perspective. A 

possible exception to the prohibition against alertnessenhancing 

compounds in civil operations could be to 

temporarily authorize these medications for pilots flying 

disaster relief or intense, but time-limited emergency 

medical flights when untreated fatigue would necessitate 

the cancellation or delay of these flights and thus 

jeopardize the safety of others. On the other hand, the 

prescription sleep-promoting compound zolpidem 

should be authorized for use by civilian commercial pilots 

in situations where quality natural sleep is difficult 

or impossible to obtain due to circadian or other reasons 

provided that: 1) the pilot has previously checked for 

any unusual reactions to the medication; 2) the dose 

does not exceed 10 mg in any given 24-h period; 3) the 

medication is used no more than 4 times in any 7-d period; 

and 4) there is an interval of 12 h between the ingestion 

of the medication and the return to duty. The 

benefits of restful sleep induced by a medication with 

short duration of action and excellent safety profile (as 

established by military aviation experience) are far preferable 

to the adverse effects of sleep deprivation when 

medication is withheld or the adverse effects of alcoholinduced 

sleep. Zolpidem should not be taken to promote 

in-flight bunk sleep or cockpit naps. To minimize complete 

reliance on medication for the improvement of 

quality preduty or postduty sleep, it is our contention 

that crewmembers should be educated about proper 

sleep hygiene, the benefits of aerobic exercise for promoting 

quality sleep, and natural strategies designed to 

promote circadian readjustment (assuming crewmembers 

will remain in a new time zone for 5 or more days). 

In the United States, the use of non-FDA regulated substances 

such as valerian, kava, and melatonin is not recommended 

because the quality of the compounds cannot 

be assured and there is insufficient scientific evidence 

of safety and/or effectiveness. In other jurisdictions, 

melatonin is available in pharmaceutical grade. In laboratory 

environments, pharmaceutical-grade melatonin 

has been effective in circadian entrainment or facilitation 

of daytime sleep (8,9,118,119,196,231). 

Fatigue detection technologies (fitness for duty and 

real-time assessment devices) and scheduling tools that 

incorporate biomathematical models of alertness can be 

incorporated as part of an overall safety management 

approach but should not be used in place of regulatory 

limitations. Prior to using any of these technologies, the 

scientific literature should be consulted to establish the 

validity of the specific technique. 

With regard to the use of prescription pharmacological 

alertness-enhancing compounds in military aviation 

operations, it is our contention that the compound dextroamphetamine 

remains an authorized option and that 

modafinil, which is already authorized by the U.S. Air 

Force, be authorized by the other services as well. Military 

flight operations are intense and unpredictable, and 

fatigued pilots often have little choice (in consideration 

of all the relevant mission factors) except to complete a 

scheduled mission. Failure to do so could jeopardize the 

safety or survivability of other military personnel or civilians. 

The benefits of appropriate stimulant use have 

been shown by scientific study to far outweigh the negative 

effects of sleep deprivation. Furthermore, proper 

medical oversight is typically available in the military 

aviation context. 

Concerning the use of prescription pharmacological 

sleep-inducing compounds in military flight operations, 

we believe the existing authorized use of temazepam, 

zolpidem, and zaleplon should be continued. Since adequate 

routine medical oversight is available in the military 

aviation context, a physician can choose the correct 

medication based on the specific situation and monitor 

for proper usage and the occurrence of unexpected side 

effects. Furthermore, it is certainly the case that the effects 

of restful sleep induced by one of the above medications 

are far superior to the effects of alcohol-induced 

sleep or to the adverse effects of sleep deprivation. 

In developing fatigue countermeasures of every sort, 

individual differences must be better addressed. There 

are differences in how people respond to sleep loss, 

sleep disruption, and time zone transitions. Research is 

focusing on identifying individual differences in sleep 

regulatory mechanisms, circadian rhythmicity, recovery 

sleep, and responses to fatigue countermeasures ( 215 , 

216 ). Examining the impact of various individual factors 

(circadian phase, sleep need, etc.) on susceptibility to 

decrements and the efficacy of countermeasures will 

facilitate optimal fatigue management in the aviation 

environment. Such data are being used for the development 

of biomathematical models of fatigue to predict 

performance and alertness levels at an individual level 

( 215 ). Due to a range of differences in how individuals 

respond to the operational challenges associated with 

long-haul and ULR flight operations, modeling work 

is also aiming to predict relative group performance for 

an overall trip pattern. Many issues associated with 

flight operations remain unanswered and can only be 

answered by collecting data during carefully scientifically 

designed research. 

In sum, while fatigue represents a significant risk in 

aviation when left unaddressed, there are currently numerous 

countermeasures and strategies that can be employed 

to increase safety. Furthermore, new technologies 

and countermeasures are being developed that hold 

great promise for the future. It is our hope that the countermeasures 

and strategies described in this paper, when 

employed appropriately, will serve to reduce the risk of 

aviation accidents and incidents attributable to the insidious 

effects of fatigue. 



ACKNOWLEDGMENTS 

The authors wish to thank Dr. Thomas Nesthus, Chair of the 

Aerospace Human Factors Committee (AHFC) for his guidance and 

support throughout a lengthy process. We are also grateful to CAPT 

Nicholas Davenport for comments and information regarding U.S. 

Navy flight duty/rest regulations and Capt. Barry Reeder for information 

about corresponding U.S. Air Force regulations though any 

errors remain ours. We thank the members of the AHFC for their comments 

on an earlier version of the manuscript, especially Dr. Ronald 

Hoffman and Dr. David Schroeder as well as the Aerospace Medical 

Association Executive Council for its comments and review, particularly 

Dr. Russell Rayman, Dr. Guillermo Salazar, Dr. Estrella Forster, 

and CAPT Christopher Armstrong. 

Authors and affiliations: John A. Caldwell, Ph.D., Archinoetics, LLC, 

Honolulu, HI; Melissa M. Mallis, Ph.D., Institutes for Behavior Resources, 

Inc.; Baltimore, MD; J. Lynn Caldwell, Ph.D., Air Force Research 

Laboratory, Wright-Patterson AFB, OH; Michel A. Paul, M.Sc., 

Defence R&D Canada (Toronto), Toronto, ON, Canada; James C. 

Miller, Ph.D., Miller Ergonomics, San Antonio, TX; and David F. Neri, 

Ph.D., Office of Naval Research, Arlington, VA. 

REFERENCES 

1. Aeronautics and Space General operating and flight rules . 14 

C.F.R. § 91.1057, 91.1059, 91.1061 (2007a). 


C.F.R. § 121 ( 2007 b) . 


C.F.R. § 135 ( 2007 c) . 

4. Afaghi A , O’Connor H , Chow CM . High-glycemic-index 

carbohydrate meals shorten sleep onset . Am J Clin Nutr 2007 ; 

85 : 426 – 30 . 

5. Ahasan R , Lewko J , Campbell D , Salmoni A . Adaptation to 

night shifts and synchronisation processes of night workers . 

J Physiol Anthropol Appl Human Sci 2001 ; 20 : 215 – 26 . 

6. Akerstedt T . Shift work and disturbed sleep/wakefulness . Occup 

Med (Lond) 2003 ; 53 : 89 – 94 . 

7. Angus RG , Pigeau RA , Heslegrave RJ . Sustained-operations 

studies: from the field to the laboratory . In: Stampi C , ed. 

Why we nap. Boston : Birkhauser ; 1992 : 217 – 41 . 

8. Arendt J . Melatonin characteristics, concerns, and prospects . 

J Biol Rhythms 2005 ; 20 : 291 – 303 . 

9. Arendt JT , Skene DJ . Melatonin as a chronobiotic . Sleep Med Rev 

2005 ; 9 : 25 – 39 . 

10. Arnulf I , Quintin P , Alvarez JC , Vigil L , Touitou Y , Lèbre AS , et al. 

Mid-morning tryptophan depletion delays REM sleep onset in 

healthy subjects . Neuropsychopharmacology 2002 ; 27 :843 –51 . 

11. Atkinson G , Edwards B , Reilly T , Waterhouse J . Exercise as a 

synchronizer of human circadian rhythms: an update and 

discussion of the methodological problems . Eur J Appl 

Physiol 2007 ; 99 : 331 – 41 . 

12. Australian Government Civil Aviation Safety Authority . Civil 

Aviation Orders. Flight time limitations – pilots Part 48, Section 

48.1, Issue 9 – December 8, 2004, Amdt. No. 29. http://www. 

casa.gov.au/download/orders/cao48/4801.pdf . 

13. Australian Government Civil Aviation Safety Authority . Rules 

watch . Flight Safety Australia 2008 ; 60 : 50 – 1 . 

14. Balter MB , Uhlenhuth EH . New epidemiologic findings about 

insomnia and its treatment . J Clin Psychiatry 1992 ; 53 ( Suppl. 

12 ): 34 – 9 . 

15. Barger LK . Wright KP , Jr , Hughes RJ , Czeisler CA . Daily exercise 

facilitates phase delays of circadian melatonin rhythm in 

very dim light . Am J Physiol Regul Integr Comp Physiol 

2004 ; 286 : R1077 – 84 Epub 2004 Mar 18. 

16. Bartholini G . Growing aspects of hypnotic drugs . In: Sauvanet 

JP , Langer SZ , Morselli PL , eds. Imidazopyridines in sleep 

disorders . New York : Raven Press ; 1988 : 1 – 9 . 

17. Belenky G , Wesensten NJ , Thorne DR , Thomas ML , Sing HC , 

Redmond DP , et al. Patterns of performance degradation and 

restoration during sleep restriction and subsequent recovery: 

a sleep dose-response study . J Sleep Res 2003 ; 12 : 1 – 12 . 

18. Belland KM , Bissell C . A subjective study of fatigue during navy 

flight operations over southern Iraq: Operation Southern 

Watch . Aviat Space Environ Med 1994 ; 65 : 557 – 61 . 

19. Belyavin A , Spencer MB . Modeling performance and alertness: 

the QinetiQ approach . Aviat Space Environ Med 2004 ; 75 ( 3, 

Suppl. ): A93 – A103 . 

20. Berka C , Levendowski DJ , Cvetinovic MM , Petrovic MM , Davis 

G , Lumicao MN , et al. Real-time analysis of EEG indexes of 

alertness, cognition, and memory acquired with a wireless 

EEG headset . Int J Hum Comput Interact 2004 ; 17 : 151 – 70 . 

21. Blois R , Gaillard J , Attali P , Coqueline J . Effect of zolpidem on 

sleep in healthy subjects: a placebo controlled trial with 

polysomnographic recordings . Clin Ther 1993 ; 15 : 797 – 809 . 

22. Bonnet MH . Dealing with shift work: physical fitness, 

temperature, and napping . Work Stress 1990 ; 4 : 261 – 74 . 

23. Bonnet MH . The effect of varying prophylactic naps on 

performance, alertness and mood throughout a 52-hour 

continuous operation . Sleep 1991 ; 14 : 307 – 15 . 

24. Bonnet MH . Acute sleep deprivation . In: Kryger MA , Roth T , 

Dement WC , eds. Principles and practice of sleep medicine . 

Philadelphia : Elsevier Saunders ; 2005 : 51 – 66 . 

25. Bonnet MH , Arand DL . Clinical effects of sleep fragmentation 

versus sleep deprivation . Sleep Med Rev 2003 ; 7 : 293 – 310 . 

26. Booth-Bourdeau J , Marcil I , Laurence M , McCulloch K , Dawson 

D. Development of fatigue risk management systems for 

the Canadian aviation industry . Proceedings of the 2005 

International Conference on Fatigue Management in 

Transportation Operations; 2005 September 11-15; Seattle. 

WA : Transport Canada ; 2005 . 

27. Boulos Z , Campbell SS , Lewy AJ , Terman M , Dijk D , Eastman CI . 

Light treatment for sleep disorders: consensus report. VI. Jet 

lag . J Biol Rhythms 1995 ; 10 : 167 – 76 . 

28. Bourgeois-Bougrine S , Carbon P , Gounelle C , Mollard R , Coblentz 

A . Perceived fatigue for short- and long-haul flights: a survey 

of 739 airline pilots . Aviat Space Environ Med 2003 ; 74 :1072 –7 . 

29. Bricknell MCM . Sleep manipulation prior to airborne exercises . 

J R Army Med Corps 1991 ; 137 : 22 – 6 . 

30. Brooks A , Lack L . A brief afternoon nap following nocturnal 

sleep restriction: which nap duration is most recuperative 

Sleep 2006 ; 29 : 831 – 40 . 

31. Brown ID . Prospectus for technological countermeasures against 

driver fatigue . Accid Anal Prev 1997 ; 29 : 525 – 31 . 

32. Brzezinski A , Vangel MG , Wurtman RJ , Norrie G , Zhdanova 

I , Ben-Shushan A , et al. Effects of exogenous melatonin on 

sleep: a meta-analysis . Sleep Med Rev 2005 ; 9 : 41 – 50 . 

33. Burgess HJ , Sharkey KM , Eastman CI . Bright light, dark and 

melatonin can promote circadian adaptation in night shift 

workers . Sleep Med Rev 2002 ; 6 : 407 – 20 . 

34. Burgess HJ , Revell VL , Eastman CI . A three pulse phase response 

curve to three milligrams of melatonin in humans . J Physiol 

2008 ; 586 : 639 – 47 . 

35. Buxton OM , Lee CW , L’Hermite-Baleriaux M , Turek FW , Van 

Cauter E . Exercise elicits phase shifts and acute alterations 

of melatonin that vary with circadian phase . Am J Physiol 

Regul Integr Comp Physiol 2003 ; 284 : R714 – 24 . 

36. Cabon P , Bourgeois-Bougrine S , Mollard R , Coblentz A , Speyer 

JJ . Electronic pilot-activity monitor: a countermeasure against 

fatigue on long-haul flights . Aviat Space Environ Med 2003 ; 

74 ( 6 Pt 1 ): 679 – 82 . 

37. Cabon P , Coblentz A , Mollard R , Fouillot JP . Human vigilance 

in railway and long-haul flight operation . Ergonomics 1993 ; 

36 : 1019 – 33 . 

38. Cajochen C . Alerting effects of light . Sleep Med Rev 2007 ; 11 : 

453 – 64 . 

39. Cajochen C , Khalsa SB , Wyatt JK , Czeisler CA , Dijk DJ . EEG and 

ocular correlates of circadian melatonin phase and human 

performance decrements during sleep loss . Am J Physiol 

1999 ; 277 : R640 – 9 . 

40. Cajochen C , Zeitzer JM , Czeisler CA , Dijk DJ . Dose 

response relationship for light intensity and ocular and 

electroencephalographic correlates of human alertness . 

Behav Brain Res 2000 ; 115 : 75 – 83 . 

41. Caldwell JA . Efficacy of stimulants for fatigue management: the 

effects of Provigil and Dexedrine on sleep-deprived aviators . 

Transportation Research Part F: Traffic Psychology and 

Behaviour 2001 ; 4 ( 1 ): 19 – 37 . 

42. Caldwell JA , Caldwell JL . An in-flight investigation of the 

efficacy of dextroamphetamine for sustaining helicopter pilot 

performance . Aviat Space Environ Med 1997 ; 68 : 1073 – 80 . 

43. Caldwell JA , Caldwell JL . Comparison of the effects of zolpideminduced 

prophylactic naps to placebo naps and forced rest 

periods in prolonged work schedules . Sleep 1998 ; 21 : 79 – 90 . 



44. Caldwell JA , Caldwell JL , Crowley JS . Sustaining female 

helicopter pilot performance with Dexedrine during 

sustained operations . Int J Aviat Psychol 1997 ; 7 : 15 – 36 . 

45. Caldwell JA , Caldwell JL , Crowley JS , Jones HD . Sustaining 

helicopter pilot performance with Dexedrine during periods 

of sleep deprivation . Aviat Space Environ Med 1995 ; 66 : 

930 – 7 . 

46. Caldwell JA , Caldwell JL , Smith JK , Alvarado L , Heintz T , Mylar 

JT , et al . The efficacy of modafinil for sustaining alertness and 

simulator flight performance in F-117 pilots during 37 hours 

of continuous wakefulness . Brooks City-Base, TX : U.S. Air 

Force Research Laboratory ; 2004 Jan. Report No. AFRL-HE- 

BR-TR-2004-0003 . 

47. Caldwell JA , Caldwell JL , Smythe NK , Hall KK . A double-blind, 

placebo-controlled investigation of the efficacy of modafinil 

for sustaining alertness and performance of aviators: a 

helicopter simulator study . Psychopharmacology (Berl) 2000 ; 

150 : 272 – 82 . 

48. Caldwell JA , Gilreath SR . A survey of aircrew fatigue in a sample 

of Army aviation personnel . Aviat Space Environ Med 2002 ; 

73 : 472 – 80 . 

49. Caldwell JA , Prazinko B , Caldwell JL . Body posture affects 

electroencephalographic activity and psychomotor 

vigilance task performance in sleep-deprived subjects . Clin 

Neurophysiol 2003 ; 114 : 23 – 31 . 

50. Caldwell JA , Smythe NK , LeDuc PA , Caldwell JL . Efficacy 

of dextroamphetamine for the maintenance of aviator 

performance during 64 hours of sustained wakefulness . 

Aviat Space Environ Med 2000 ; 71 : 7 – 18 . 

51. Caldwell JL , Gilreath SR . Work and sleep hours of U.S. Army 

aviation personnel working reverse cycle . Mil Med 2001 ; 

166 : 159 – 66 . 

52. Caldwell JL , Prazinko BF , Rowe T , Norman D , Hall KK , 

Caldwell JA . Improving daytime sleep with temazepam as a 

countermeasure for shift lag . Aviat Space Environ Med 2003 ; 

74 : 153 – 63 . 

53. Carskadon MA . Ontogeny of human sleepiness as measured by 

sleep latency . In: Dinges DF , Broughton RJ , eds. Sleep and 

alertness: chronobiological, behavioral, and medical aspects 

of napping New York : Raven Press ; 1989 : 53 – 69 . 

54. Chagan L , Cicero LA . Zaleplon: A possible advance in the 

treatment of insomnia . P&T 1999 ; 24 : 590 – 9 . 

55. Co EL . Gregory KB , Johnson JM , & Rosekind MR . Crew factors 

in flight operations XI: A survey of fatigue factors in regional 

airline operations. Moffett Field, CA : NASA Ames Research 

Center ; 1999 . Report No: NASA/TM – 1999 – 208799 . 

56. Committee on Military Nutrition Research . Caffeine for the 

sustainment of mental task performance: Formulations for 

military operations . Washington, DC : National Academy 

Press 2001 . 

57. Comperatore CA , Caldwell JA , Caldwell JL . Leader’s guide 

to crew endurance. Instructional brochure on crew work/ 

rest scheduling, circadian rhythms, fatigue, and fatigue 

countermeasures . Fort Rucker, AL : U.S. Army Aeromedical 

Research Laboratory and the U.S. Army Safety Center , 1997 . 

58. Cornum KG , Cornum R , Storm W . Use of psychostimulants in 

extended flight operations: a Desert Shield experience . In: 

Advisory Group for Aerospace Research and Development 

Conference Proceedings No. 579, Neurological Limitations 

of Aircraft Operations: Human Performance Implications . 

Neuilly-sur-Seine, France : NATO Advisory Group for 

Aerospace Research and Development ; 1996 : 371 – 4 . 

59. Cornum R , Caldwell JA , Cornum KG . Stimulant use in extended 

flight operations . Airpower J 1997 ; 11 ( 1 ): 53 – 8 . 

60. Cosenzo KA , Fatkin LT , Patton DJ . Ready or not: enhancing 

operational effectiveness through use of readiness measures . 

Aviat Space Environ Med 2007 ; 75 ( 5, Suppl. ): B96 – 106 . 

61. Costa G . The problem: shiftwork . Chronobiol Int 1997 ; 14 : 89 – 98 . 

62. Daan S , Lewy AJ . Scheduled exposure to daylight: a potential 

strategy to reduce “ jet lag ” following transmeridian flight . 

Psychopharmacol Bull 1984 ; 20 : 566 – 8 . 

63. Dijk DJ , Franken P. Interaction of sleep homeostasis and 

circadian rhythmicity : dependent or independent systems 

In: Kryger MA , Roth T , Dement WC , eds. Principles and 

practice of sleep medicine. Philadelphia: Elsevier Saunders; 

2005: 418 – 434 . 

64. Dijkman M , Sachs N , Levine E , Mallis M , Carlin MM , Gillen KA , 

et al. Effects of reduced stimulation on neurobehavioral 

alertness depend on circadian phase during human sleep 

deprivation . Sleep Res 1997 ; 26 : 265 . 

65. Dinges DF . Differential effects of prior wakefulness and circadian 

phase on nap sleep . Electroencephalogr Clin Neurophysiol 

1986 ; 64 : 224 – 7 . 

66. Dinges DF . Critical research issues in development of 

biomathematical models of fatigue and performance . Aviat 

Space Environ Med 2004 ; 75( 3, Suppl) A181 – 91 . 

67. Dinges DF , Graeber RC , Rosekind MR , Samel A , Wegmann 

HM. Principles and guidelines for duty and rest scheduling 

in commercial aviation. Moffett Field, CA: NASA Ames 

Research Center; 1996. Report No: 110404 . 

68. Dinges DF , Maislin G , Brewster RM , Krueger GP , Carroll RJ . Pilot 

test of fatigue management technologies. Washington, DC: 

Transportation Research Board of the National Academies, 

Journal of the Transportation Research Board ; 2005 Report 

No. 1922 . 

69. Dinges DF , Mallis MM. Managing fatigue by drowsiness 

detection : can technological promises be realized In: Hartley 

L , eds. Managing fatigue in transportation. Kidlington, 

Oxford, UK: Elsevier Science Ltd; 1998: 209 – 29 . 

70. Dinges DF , Mallis MM , Maislin G , Powell JW. Final report: 

evaluation of techniques for ocular measurement as an index of 

fatigue and as the basis for alertness management. Washington, 

DC: National Highway Traffic Safety Administration; 1998 

Report No: DOT HS 808 762 . 

71. Dinges DF , Orne MT , Orne EC . Assessing performance upon 

abrupt awakening from naps during quasi-continuous 

operations . Behav Res Methods Inst Comput 1985 ; 17 : 37 – 45 . 

72. Dinges DF , Price NJ , Maislin G , Powell JW , Ecker AJ , Mallis 

MM . Szuba, et al. Prospective laboratory re-validation 

of ocular-based drowsiness detection technologies and 

countermeasures. In: Wierwille WW , Hanowski RJ , Olson RL , 

Dinges DF , Price NJ , Maislin G , et al. NHTSA Drowsy Driver 

Detection And Interface Project: Subtask A; 2002; Report No: 

DTNH 22-00-D-07007 . 

73. Dinges DF , Rider RL , Dorrian J , McGlinchey EL , Rogers NL , Cizman 

Z , et al. Optical computer recognition of facial expressions 

associated with stress induced by performance demands . Aviat 

Space Environ Med 2005 ; 76 (6, Suppl)B172 –82. 

74. Dinges DF , Whitehouse WG , Orne EC , Orne MT . The benefits of 

a nap during prolonged work and wakefulness . Work Stress 

1988 ; 2 : 139 – 53 . 

75. Driskell JE , Mullen B . The efficacy of naps as a fatigue 

countermeasure: a meta-analytic integration . Hum Factors 

2005 ; 47 : 360 – 77 . 

76. Driver HS , Taylor SR . Sleep and exercise . Sleep Med Rev 2000 ; 

4 : 387 – 402 . 

77. Duffy JF , Wright KP . Entrainment of the human circadian system 

by light . J Biol Rhythms 2005 ; 20 : 326 – 38 . 

78. Eastman CI , Boulos Z , Terman M , Campbell SS , Dijk D , Lewy 

AJ . Light treatment for sleep disorders: consensus report. VI. 

shift work . J Biol Rhythms 1995 ; 10 : 157 – 64 . 

79. Ebert B , Wafford KA , Deacon S . Treating insomnia: current and 

investigational pharmacological approaches . Pharmacol Ther 

2006 ; 112 : 612 – 29 . 

80. Elie R , Ruther E , Farr I , Emilien G , Salinas E . Sleep latency is 

shortened during 4 weeks of treatment with zaleplon, a novel 

nonbenzodiazepine hypnotic . J Clin Psychiatry 1999 ; 60 : 

536 – 44 . 

81. Emonson DL , Vanderbeek RD . The use of amphetamine in U.S. 

Air Force tactical operations during Desert Shield and Storm . 


82. Fabiani M , Gratton G , Coles MG Event-related brain potentials 

In: Caciooppo JT , Tassinary LG , Berntson GG, eds. 

Handbook of psychophysiology . Cambridge, England: 

Cambridge University Press; 2000: 53 – 84 . 

83. Flight Safety Foundation. Lessons from the dawn of ultra-longrange 

flight . Flight Saf Dig 2005; Aug-Sept: 1 – 60 . 

84. Folkard S , Tucker P . Shift work, safety and productivity . Occup 

Med 2003 ; 53 : 95 – 101 . 

85. Fry J , Scharf M , Mangano R , Fujimori M . Zaleplon improves 

sleep without producing rebound effects in outpatients with 

insomnia . Int Clin Psychopharmacol 2000 ; 15 : 141 – 52 . 



86. Galinsky T , Swanson N , Sauter S , Dunkin R , Hurrell J , Schleifer 

L . Supplementary breaks and stretching exercises for data 

entry operators: a follow-up field study . Am J Ind Med 2007 ; 

50 : 519 – 27 . 

87. Gander PH , Graeber RC , Connell LJ , Gregory KB. Crew factors 

in flight operations VIII: factors influencing sleep timing and 

subjective sleep quality in commercial long-haul flight crews. 

Moffett Field, CA: NASA; 1991. Technical Memorandum 

103852. 

88. Gander PH , Myhre G , Graeber RC , Anderson HT , Lauber JK . 

Adjustment of sleep and the circadian temperature rhythm 

after flights across nine time zones . Aviat Space Environ Med 

1989 ; 60 : 733 – 43 . 

89. Gillberg M . The effects of two alternative timings of a one-hour nap 

on early morning performance . Biol Psychol 1984 ; 19 :45 –54 . 

90. Gillberg M . Sleepiness and its relation to the length, content, and 

continuity of sleep . J Sleep Res 1995 ; 4 ( Suppl. 2): 37 – 40 . 

91. Gilliland K , Schlegel RE . Readiness to perform: a critical analysis 

of the concept and current practices. Oklahoma City, OK: 

Office of Aviation Medicine, Federal Aviation Administration . 

NTIS No. AD 1993 ; A269 : 379 . 

92. Goldsmith C . More carriers sanction their pilots ’ cockpit snoozes . 

The Wall Street Journal 1998 Jan 21 , B1 . 

93. Greenblatt DJ , Zammit G , Harmatz J , Legangneux E . Zolpidem 

modified-release demonstrates sustained and greater 

pharmacodynamic effects from 3 to 6 hours postdose as 

compared with standard zolpidem in healthy adult subjects. 

[Abstract] Sleep 2005 ; 28 (Suppl.): A245 . 

94. Gu H , Ji Q. An automated face reader for fatigue detection. 

Proceedings of the Sixth IEEE International Conference 

on Automatic Face and Gesture Recognition; 2004. Los 

Alamitos, CA: IEEE; 2004:111–6. 

95. Hadley S , Petry JJ . Valerian . Am Fam Physician 2003 ; 67 : 1755 – 8 . 

96. Heslegrave RJ , Angus RG . The effects of task duration and worksession 

location on performance degradation induced by 

sleep loss and sustained cognitive work . Behav Res Methods 

Inst Comput 1985 ; 17 : 592 – 603 . 

97. Ho P , Landsberger S , Signal L , Singh J , Stone B . The Singapore 

experience: task force studies scientific data to assess flights . 

Flight Safety Digest 2005 ; 24(8–9) : 20 – 40. 

98. Horne JA , Foster SC . Can exercise overcome sleepiness 

[Abstract] Sleep Research 1995 ; 24A : 437 . 

99. Horowitz TS , Tanigawa T . Circadian-based new technologies for 

night workers. Ind Health 2002; 40:223–36 . 

100. Hursh SR , Raslear TG , Kaye SA , Fanzone JF Jr. Validation and 

calibration of a fatigue assessment tool for railroad work 

schedules, summary report. Washington, DC: Department 

of Transportation; 2006 ; DOT/FRA/ORD-06/21 , October 31 , 

2006. 

101. Hursh SR, Redmond DP, Johnson ML, Thorne DR, Belenky 

TJ, Storm WF , et al. Fatigue models for applied research in 

warfighting. Aviat Space Environ Med 2004; 75 (3, Suppl.) : 

A44-A53 . 

102. Ji Q , Zhu Z , Lan P . Real-time nonintrusive monitoring and 

prediction of driver fatigue Vehicular Technology . IEEE 

Transactions 2004 ; 53 : 1052 – 68 . 

103. Kirsch AD . Report on the statistical methods employed by the U.S. 

Federal Aviation Administration in its cost/benefit analysis 

of the proposed flight crewmember duty period limitations, 

flight time limitations and rest requirements. Washington, 

DC; United States Federal Aviation Administration; 1996. 

Docket No: 28081. 

104. Kithil PW , Jones RD , MacCuish J . Development of driver 

alertness detection system using overhead capacitive sensor 

array . 2006; Retrieved from http://internet.cybermesa.com/ 

;roger_jones/drowsy.htm . 

105. Klein KE , Bruner H , Holtmann H , Rehme H , Stolze J , Steinhoff 

WD , et al. Circadian rhythm of pilots ’ efficiency and effects 

of multiple time zone travel . Aerosp Med 1970 ; 41 : 125 – 32 . 

106. Klein KE , Wegmann HM . Significance of circadian rhythms in 

aerospace operations . AGARDograph No. 247 , 1980. Neuillysur-Seine, 

France . 

107. Krystal AD , Erman M , Zammit GK , Soubrane C , Roth T; 

ZOLONG Study Group. Long-term efficacy and safety 

of zolpidem extended-release 12.5 mg, administered 3 to 

7 nights per week for 24 weeks, in patients with chronic 

primary insomnia: a 6-month, randomized, double-blind, 

placebo-controlled, parallel-group, multicenter study . Sleep 

2008 ; 31 : 79 – 90 . 

108. Lagarde D , Batejat D . Disrupted sleep-wake rhythm and 

performance: Advantages of modafinil . Mil Psychol 1995 ; 

7 : 165 – 91 . 

109. Lal SKL , Craig A . Reproducibility of the spectral components 

of the electroencephalogram during driver fatigue . Int J 

Psychophysiol 2005 ; 55 : 137 – 43 . 

110. Landström U , Knutsson A , Lennernäs M , Söderberg L . Laboratory 

studies of the effects of carbohydrate consumption on 

wakefulness . Nutr Health 2000 ; 13 : 213 – 25 . 

111. Lavie P . Ultrashort sleep-waking schedule. III. “ Gates ” and 

“ forbidden zones ” for sleep . Electroencephalogr Clin 

Neurophysiol 1986 ; 63 : 414 – 25 . 

112. Lavine RA , Sibert JL , Gokturk M , Dickens B . Eye-tracking 

measures and human performance in a vigilance task . Aviat 

Space Environ Med 2002 ; 73 : 367 – 72 . 

113. LeDuc PA , Caldwell JA , Ruyak PS . The effects of exercise versus 

napping on alertness and mood in sleep-deprived aviators. 

Fort Rucker, AL: U.S. Aeromedical Research Laboratory; 

2000; Technical Report 2000 – 12 . 

114. Leese P , Maier G , Vaickus L , Akylbekova E . Esopiclone: 

pharmacokinetic and pharmacodynamic effects of a novel 

sedative hypnotic after daytime administration in healthy 

subjects.[Abstract] Sleep 2002 ; 25( Suppl.): A45 . 

115. Levendowski DJ , Berka C , Olmstead RE , Jarvik M . Correlations 

between EEG indices of alertness measures of performance 

and self-reported states while operating a driving simulator. 

[Abstract]. 29th Annual Meeting, Society for Neuroscience; 

1999 October 25; Miami Beach, FL . Washington, DC Soceity 

for Neuroscience ; 1999 ; Vol. 25 . 

116. Levendowski DJ , Olmstead RE , Konstantinovic ZR , Berka C , 

Westbrook PR . Detection of electroencephalographic indices 

of drowsiness in real time using a multi-level discriminant 

function analysis . Sleep 2000; 23 (Abstract Suppl. 2): A243 – 4 

117. Lewy AJ , Bauer VK , Ahmed S , Thomas KH , Cutler NL , Singer 

CM , et al. The human phase response curve (PRC) to 

melatonin is about 12 hours out of phase with the PRC to 

light . Chronobiol Int 1998 ; 15 : 71 – 83 . 

118. Lewy AJ , Emens J , Jackman A , Yuhas K . Circadian uses of 

melatonin in humans . Chronobiol Int 2006 ; 23 : 403 – 12 . 

119. Lieberman JA . Update on the safety considerations in the 

management of insomnia with hypnotics: Incorporating 

modified-release formulations into primary care . Prim Care 

Companion J Clin Psychiatry 2007 ; 9 : 25 – 31 . 

120. Lin C , Wu R , Jung T , Liang S , Huang T . Estimating driving 

performance based on EEG spectrum analysis. EURASIP J 

Appl Signal Processing 2005 ; 19 : 3165 – 74 . 

121. Lobb ML , Stern JA . Pattern of eyelid motion predictive of 

decision errors during drowsiness: oculomotor indices of 

altered states . Int J Neurosci 1986 ; 30 : 17-22. 

122. Lockley SW , Evans EE , Scheer FA , Brainard GC , Czeisler CA , 

Aeschbach D . Short-wavelength sensitivity for the direct 

effects of light on alertness, vigilance, and the waking 

electroencephalogram in humans . Sleep 2006 ; 29 : 161 – 8 . 

123. Lucero K , Hicks RA . Relationship between habitual sleep 

duration and diet . Percept Mot Skills 1990 ; 71( 3 Pt 2): 1377 – 8 . 

124. Luna T . Fatigue in context: USAF mishap experience. [Abstract] 

Aviat Space Environ Med 2003 ; 74 : 388 . 

125. Mallis M , Maislin G , Konowal N , Byrne V , Bierman D , Davis 

R , et al. Biobehavioral responses to drowsy driving alarms 

and alerting stimuli. Washington, DC : U.S. Department of 

Transportation; 1998; Final Report : 1 – 127 . 

126. Mallis MM , Mejdal S , Nguyen TT , Dinges DF . Summary of the key 

features of seven biomathematical models of human fatigue 

and performance . Aviat Space Environ Med 2004 ; 75 :A4 –14 . 

127. Mallis MM, Neri DF, Colletti LM, Oyung RL, Reduta DD, Van 

Dongen H , et al. Feasibility of an automated drowsiness 

monitoring device on the flightdeck. Sleep 2004; 27 (Abstract 

Suppl.): A167-8 . 

128. Matsumoto K , Harada M . The effect of night-time naps on 

recovery from fatigue following night work . Ergonomics 

1994 ; 37 : 899 – 907 . 

129. Matsumoto Y , Mishima K , Satoh K , Shimizu T , Hishikawa Y . 

Physical activity increases the dissociation between subjective 



sleepiness and objective performance levels during extended 

wakefulness in human . Neurosci Lett 2002 ; 326 : 133 – 6 . 

130. Melfi ML , Miller JC. Causes and effects of fatigue in experienced 

military aircrew and the countermeasures needed to improve 

flight safety. Brooks City-Base, TX : Air Force Research 

Laboratory; 2006 Jan. Report No AFRL-HE-BR-TR-2006-0071 . 

131. Menkes DB. Hypnosedatives and anxiolytics . In: Dukes MNG , 

Aronson JK, eds. Meyler’s side effects of drugs , 14th ed. 

Amsterdam : Elsevier Science; 2000 : 121 – 38 . 

132. Mitler MM , Aldrich MS . Stimulants: efficacy and adverse 

effects. In: Kryger MH , Roth T , Dement WC, eds. Principles 

and practice of sleep medicine. 3rd ed. Philadelphia: W.B. 

Saunders Co; 2000 : 429 – 40 . 

133. Mitler MM , Carskadon MA , Phillips RL , Sterling WR , Zarcone 

VP , Jr ., Spiegels R , et al. Hypnotic efficacy of temazepam: a 

long-term sleep laboratory evaluation . Br J Clin Pharmacol 

1979 ; 8 : 63S – 8S . 

134. Mohler SR . Clinical problems in aviation medicine: fatigue in 

aviation activities . Aerosp Med 1966 ; 37 : 722 – 32 . 

135. Moja EA , Antinoro E , Cesa-Bianchi M , Gessa GL . Increase in 

stage 4 sleep after ingestion of a tryptophan-free diet in 

humans . Pharmacol Res Commun 1984 ; 16 : 909 – 14 . 

136. Monti JM . Primary and secondary insomnia: prevalence, causes 

and current therapeutics . Curr Med Chem Cent Nerv Syst 

Agents 2004 ; 4 : 119 – 37 . 

137. Morin AK . Strategies for treating chronic insomnia . Am J Manag 

Care 2006 ; 12 : S230 – 46 . 

138. Muller FO , Dyk MV , Hundt HKL , Joubert AL , Luus HG , 

Groenewoud G , et al. Pharmacokinetics of temazepam after 

day-time and night-time oral administration . Eur J Clin 

Pharmacol 1987 ; 33 : 211 – 4 . 

139. National Transportation Safety Board. A review of flightcrewinvolved, 

major accidents of U.S. air carriers, 1978 through 

1990. Washington, DC: National Transportation Safety Board; 

1994. Report No: NTSB Safety Study No. SS-94-01. 

140. National Transportation Safety Board’s Most Wanted Aviation 

Safety Improvements: Hearing before the Subcommittee 

on Aviation of the Committee on Transportation and 

Infrastructure, 110 th Cong., 1 st Sess., 35 – 37 (2007) (testimony 

of William R. Voss). 

141. National Sleep Foundation. 2002 Sleep in America poll. 

Washington: National Sleep Foundation 2002. 

142. Nehlig A . Are we dependent upon coffee and caffeine a review 

on human and animal data . Neurosci Biobehav Rev 1999 ; 

23 : 563 – 76 . 

143. Neri DF . Scientific and operational issues associated with ultra 

long range flight [Abstract] . Aviat Space Environ Med 2005 ; 

76 : 247 

144. Neri DF , Oyung RL , Colletti LM , Mallis MM , Tam PY , Dinges DF . 

Controlled breaks as a fatigue countermeasure on the flight 

deck . Aviat Space Environ Med 2002 ; 73 : 654 – 64 . 

145. Neri DF , Wiegmann D , Stanny RR , Shappell SA , McCardie A , 

McKay DL . The effects of tyrosine on cognitive performance 

during extended wakefulness . Aviat Space Environ Med 

1995 ; 66 : 313 – 9 . 

146. Neumann M , Jacobs KW . Relationship between dietary 

components and aspects of sleep . Percept Mot Skills 1992 ; 

75 ( 3 Pt 1 ): 873 – 4 . 

147. Neville KJ , Bisson RU , French J , Boll PA , Storm WF . Subjective 

fatigue of C-141 aircrews during Operation Desert Storm . 

Hum Factors 1994 ; 36 : 339 – 49 . 

148. Newhouse PA , Penetar DM , Fertig JB , Thorne DR , Sing HC , 

Thomas ML , et al. Stimulant drug effects on performance and 

behavior after prolonged sleep deprivation: a comparison of 

amphetamine, nicotine, and deprenyl . Mil Psychol 1992 ; 4 : 

207 – 33 . 

149. Nicholson AN . Hypnotics and occupational medicine . J Occup 

Med 1990 ; 32 : 335 – 41 . 

150. Nicholson AN , Pascoe PA , Spencer MB , Stone BM , Roehrs TA , 

Roth T . Sleep after transmeridian flights . Lancet 1986 ; 2 : 

1205 – 8 . 

151. Nicholson AN , Roth T , Stone BM . Hypnotics and aircrew . Aviat 


152. Nicholson AN, Stone BM. Sleep and wakefulness handbook for 

flight medical officers. Neuilly-sur-Seine, France: Advisory 

Group for Aerospace Research and Development; 1982. 

153. Nicholson AN , Stone BM , Pascoe PA . Efficacy of some 

benzodiazepines for day-time sleep . Br J Clin Pharmacol 

1980 ; 10 : 459 – 63 . 

154. Oren DA , Reich W , Rosenthal NE , Wehr TA . How to beat jet lag: 

a practical guide for air travelers . New York : Henry Holt ; 

1993 . 

155. Owasoyo JO , Neri DF , Lamberth JG . Tyrosine and its potential 

use as a countermeasure to performance decrement in 

military sustained operations . Aviat Space Environ Med 

1992 ; 63 : 364 – 9 . 

156. Palminteri R , Narbonne G . Safety profile of zolpidem . In: 

Sauvanet JP , Langer SZ , Morselli PL , eds. Imidazopyridines 

in sleep disorders . New York : Raven Press ; 1988 : 351 – 60 . 

157. Paul MA , Gray G , Kenny G , Pigeau R . Impact of melatonin, 

zaleplon, zopiclone, and temazepam on psychomotor 

performance . Aviat Space Environ Med 2003 ; 74 :1263 –70 . 

158. Paul MA , Gray G , MacLellan M , Pigeau RA . Sleep-inducing 

pharmaceuticals: a comparison of melatonin, zaleplon, 

zopiclone, and temazepam . Aviat Space Environ Med 2004 ; 

75 : 512 – 9 . 

159. Physician’s Desk Reference. Modafinil. In: Physician’s Desk 

Reference. Montvale, NJ: Thomson PDR; 2003:1193-6. 

160. Pigeau R , Naitoh P , Buguet A , McCann C , Baranski J , Taylor 

M , et al. Modafinil, d-amphetamine and placebo during 64 

hours of sustained mental work. effects on mood, fatigue, 

cognitive performance and body temperature . J Sleep Res 

1995 ; 4 : 212 – 28 . 

161. PMI, Inc. FIT Workplace Safety Screener: theory and validation. 

Rockville, MD: PMI, Inc 1999. 

162. Porcu S , Bellatreccia A , Ferrara M , Casagrande M . Performance, 

ability to stay awake, and tendency to fall asleep during the 

night after a diurnal sleep with temazepam or placebo . Sleep 

1997 ; 20 : 535 – 41 . 

163. Portas CM , Bjorvatn B , Ursin R . Serotonin and the sleep/wake 

cycle: special emphasis on microdialysis studies . Prog 

Neurobiol 2000 ; 60 : 13 – 35 . 

164. Porter JM , Horne JA . Bed-time food supplements and sleep: 

effects of different carbohydrate levels . Electroencephalogr 

Clin Neurophysiol 1981 ; 51 : 426 – 33 . 

165. Prazinko BF , Sam JA , Caldwell JL , Townsend AT . Dose 

uniformity of over-the-counter melatonin as determined by 

high-pressure liquid chromatography . Fort Rucker, AL : U. 

S. Army Aeromedical Research Laboratory ; 2000 ; USAARL 

Technical Report 2000 – 23 . 

166. Ramsey CS , McGlohn SE . Zolpidem as a fatigue countermeasure . 


167. Reid KJ , Burgess HJ . Circadian rhythm sleep disorders . Prim 

Care 2005 ; 32 : 449 – 73 . 

168. Revell VL , Eastman CI . How to trick Mother Nature into letting 

you fly around or stay up all night . J Biol Rhythms 2005 ; 

20 : 353 – 65 . 

169. Robertson P , Hillriegel ET . Clinical pharmacokinetic profile of 

modafinil . Clin Pharmacokinet 2003 ; 42 : 123 – 37 . 

170. Roehrs T , Burduvali E , Bonahoom A , Drake C , Roth T . Ethanol 

and sleep loss: a “ dose ” comparison of impairing effects . 

Sleep 2003 ; 26 : 981 – 5 . 

171. Rogers AS , Spencer MB , Stone BM , Nicholson AN . The influence 

of a 1 h nap on performance overnight . Ergonomics 1989 ; 

32 : 1193 – 205 . 

172. Roky R , Chapatot F , Benchekroun MT , Benaji B , Hakkou F , 

Elkhalifi H , et al. Daytime sleepiness during Ramadan 

intermittent fasting: polysomnographic and quantitative 

waking EEG study . J Sleep Res 2003 ; 12 : 95 – 101 . 

173. Roky R , Chapatot F , Hakkou F , Benchekroun MT , Benaji B , 

Buguet A . Sleep during Ramadan intermittent fasting . J Sleep 

Res 2001 ; 10 : 319 – 27 . 

174. Rosa RR . Napping at home and alertness on the job in rotating 

shift workers . Sleep 1993 ; 16 : 727 – 35 . 

175. Rosekind MR , Co EL , Gregory KB , Miller DL . Crew factors 

in flight operations XIII: a survey of fatigue factors in 

corporate/executive aviation operations . Moffett Field, CA : 

NASA Ames Research Center ; 2000 . Report No .: NASA/TM – 

2000 – 209610 . 

176. Rosekind MR , Gander PH , Connell LJ , Co EL . Crew factors 

in flight operations X: alertness management in flight 

operations education module . Moffett Field, California : 



National Aeronautics and Space Administration ; 2001 ; NASA 

Technical Memorandum No. 2001 - 211385 . 

177. Rosekind MR , Graeber RC , Dinges DF , Connell LJ , Rountree 

MS , Spinweber CL , et al. Crew factors in flight operations 

IX : effects of planned cockpit rest on crew performance 

and alertness in long-haul operations . Moffett Field, CA : 

NASA Ames Research Center ; 1994 ; Report No: DOT/ 

FAA/92/24. 

178. Rosekind MR , Gregory KB , Miller DL , Co EI , Lebacqz JV , Brenner 

M . Crew fatigue factors in the Guantanamo Bay aviation 

accident. [Abstract] Sleep Res 1996 ; 25 : 571 . 

179. Rosekind MR , Miller DL , Gregory KB , Dinges DF . Crew factors 

in flight operations XII: a survey of sleep quantity and quality 

in on-board crew rest facilities . Moffett Field, CA : NASA ; 

2000 ; Report No: NASA/TM-2000-20961 . 

180. Roth T , Piccione P , Salis P , Kramer M , Kaffeman M . Effects of 

temazepam, flurazepam and quinalbarbitone on sleep: 

psychomotor and cognitive function . Br J Clin Pharmacol 

1979 ; 8 : 47S – 54S . 

181. Roth T , Roehrs T . A review of the safety profiles of benzodiazepine 

hypnotics . J Clin Psychiatry 1991 ; 52 ( 9, Suppl ) 38 – 47 . 

182. Rowland L , Thomas M , Thorne D , Sing H , Davis HQ , Redmond 

D , et al. Oculomotor changes during 64 hours of sleep. 

[Abstract] Sleep Res 1997 ; 26 : 626 . 

183. Russo M , Thomas M , Sing H , Thorne D , Balkin T , Wesensten N , 

et al. Saccadic velocity and pupil constriction latency changes 

in partial sleep deprivation, and correlations with simulated 

motor vehicle crashes . Sleep 1999 ; 22 ( Suppl. 1 ): S297 – 8 . 

184. Russo M , Thomas M , Thorne D , Sing H , Redmond D , Rowland 

L , et al. Oculomotor impairment during chronic partial 

sleep deprivation. Elsevier Science Ireland, Ltd . for the 

International Federation of Clinical Neurophysiology , 2003 ; 

114 : 723 – 736 . 

185. Sack RL , Auckley D , Auger RR , Carskadon MA , Wright KP , 

Jr ., Vitiello MV , et al. Circadian rhythm sleep disorders: 

part I, basic principles, shift work and jet lag disorders. An 

American Academy of Sleep Medicine review . Sleep 2007 ; 

30 : 1460 – 83 . 

186. Samel A , Wegmann HM , Vejvoda M . Jet lag and sleepiness in 

aircrew . J Sleep Res 1995 ; 4 ( S2 ): 30 – 6 . 

187. Samel A , Wegmann HM , Vejvoda M . Aircrew fatigue in longhaul 

operations . Accid Anal Prev 1997 ; 29 : 439 – 52 . 

188. Sanger DJ , Perrault G , Morel E , Joly D , Zivkovic B . The 

behavioral profile of zolpidem, a novel hypnotic drug of 

imidazopyridine structure . Physiol Behav 1987 ; 41 : 235 – 40 . 

189. Schultz D , Miller JC . Fatigue and use of go/no-go pills in 

extraordinarily long combat sorties [Commentary]. 

Aviat 


190. Schultz D , Miller JC . Fatigue and use of go/no go pills in F-16 

pilots subjected to extraordinarily long combat sorties Brooks 

City-Base, TX : Air Force Research Laboratory ; 2004 Apr. ; 

Technical report: AFRL-HE-BR-TR-2004-0014 . 

191. Schweitzer PK , Muehlback MJ , Walsh JK . Countermeasures for 

night work performance deficits: the effect of napping or 

caffeine on continuous performance at night . Work Stress 1992 ; 

6 :355–65. 

192. Senechal PK . Flight surgeon support of combat operations at RAF 

Upper Heyford . Aviat Space Environ Med 1988 ; 59 :776–7. 

193. Shiota M , Sudou M , Ohshima M . Using outdoor exercise to 

decrease jet lag in airline crewmembers . Aviat Space Environ 

Med 1996 ; 67 : 1155 – 60 . 

194. Signal L , Gander P , van den Berg M . Sleep during ultra-long 

range flights: a study of sleep on board the 777-200 ER during 

rest opportunities of 7 hours. Report Published for the Boeing 

Commercial Airplane Group Sleep/Wake Research Centre , 

Massey University . Wellington, New Zealand : 2003 . 

195. Signal L , Ratieta D , Gander P . Fatigue management in the New 

Zealand aviation industry . Australian Transport Safety 

Bureau Research and Analysis Report April, 2006 . 

196. Skene DJ , Arnedt J . Human circadian rhythms: physiological 

and therapeutic relevance of light and melatonin . Ann Clin 

Biochem 2006 ; 43 : 344 – 53 . 

197. Spring B , Maller O , Wurtman J , Digman L , Cozolino L . Effects of 

protein and carbohydrate meals on mood and performance: 

interactions with sex and age . J Psychiatr Res 1982-1983 ; 

17 : 155 – 67 . 

198. Spurgeon A . Working time: its impact on safety and health. 

International Labour Office Report . Geneva : International 

Labour Organization , 2003 . 

199. Stepanski EJ , Wyatt JK . Use of sleep hygiene in the treatment of 

insomnia . Sleep Med Rev 2003 ; 7 : 215 – 25 . 

200. Stewart S , Holmes A , Jackson P , Abboud R . An integrated 

system for managing fatigue risk within a low cost carrier. 

Enhancing Safety Worldwide: Proceedings of the 59 th annual 

IASS ; 2006 Oct 23-25 ; Paris, France . Alexandria, VA : Flight 

Safety Foundation ; 2006 . 

201. Stone BM , Turner C . Promoting sleep in shiftworkers and 

intercontinental travelers . Chronobiol Int 1997 ; 14 : 133 – 43 . 

202. Suhner A , Schlagenhauf P , Hofer I , Johnson R , Tschopp A , Steffen 

R . Effectiveness and tolerability of melatonin and zolpidem 

for the alleviation of jet lag . Aviat Space Environ Med 2001 ; 

72 : 638 – 46 . 

203. Taibi DM , Landis CA , Petry H , Vitiello MV . A systematic review 

of valerian as a sleep aid: safe but not effective . Sleep Med 

Rev 2007 ; 11 : 209 – 30 . 

204. Tietzel AJ , Lack LC . The short-term benefits of brief and long 

naps following nocturnal sleep restriction . Sleep 2001 ; 

24 : 293 – 300 . 

205. Tilley AJ , Wilkinson RT , Warren PSG , Watson B , Drud M . The 

sleep and performance of shift workers . Hum Factors 1982 ; 

24 : 629 – 41 . 

206. Touitou Y , Bogdan A . Promoting adjustment of the sleep-wake 

cycle by chronobiotics . Physiol Behav 2007 ; 90 : 294 – 300 . 

207. Tsai YF , Viirre E , Strychacz C , Chase B , Jung TP . Task performance 

and eye activity: predicting behavior relating to cognitive 

workload . Aviat Space Environ Med 2007 ; 78 ( 5, Suppl ) 

B176 – 85 . 

208. Tucker P , Folkard S , Macdonald I . Rest breaks and accident risk . 

Lancet 2003 ; 361 ( 9358 ): 680 . 

209. U.S. National Library of Medicine and the National Institutes 

of Health. Drug information: Temazepam. In: Medline Plus; 

2004. www.nlm.nih.gov/medlineplus/ 

210. Navy US . Performance maintenance during continuous flight 

operations — a guide for flight surgeons . Fallon, NV : Naval 

Strike and Air Warfare Center ; 2000 . 

211. Van den Heuvel CJ , Ferguson SA , Macchi MM , Dawson D . 

Melatonin as a hypnotic: con . Sleep Med Rev 2005 ; 9 : 71 – 80 . 

212. Van Dongen HPA . Comparison of mathematical model 

predictions to experimental data of fatigue and performance . 

Aviat Space Environ Med 2004 ; 75 ( 3, Suppl ) A122 – 4 . 

213. Van Dongen HP , Dinges DF . Sleep, circadian rhythms, and 

psychomotor vigilance . Clin Sports Med 2005 ; 24 : 237 – 49 (viiviii.) 

. 

214. Van Dongen HPA , Maislin G , Mullington JM , Dinges DF . The 

cumulative cost of additional wakefulness: Dose-response 

effects on neurobehavioral functions and sleep physiology 

from chronic sleep restriction and total sleep deprivation . 

Sleep 2003 ; 26 : 117 – 26 . 

215. Van Dongen HP , Mott CG , Huang JK , Mollicone DJ , McKenzie 

FD , Dinges DF . Optimization of biomathematical model 

predictions for cognitive performance impairment in 

individuals: accounting for unknown traits and uncertain 

states in homeostatic and circadian processes . Sleep 2007 ; 

30 : 1129 – 43 . 

216. Van Dongen HP , Vitellaro KM , Dinges DF . Individual differences 

in adult human sleep and wakefulness: Leitmotif for a 

research agenda . Sleep 2005 ; 28 : 479 – 96 . 

217. Vgontzas AN , Pejovic S , Zoumakis E , Lin HM , Bixler EO , Basta 

M , et al. Daytime napping after a night of sleep loss decreases 

sleepiness, improves performance, and causes beneficial 

changes in cortisol and interleukin-6 secretion . Am J Physiol 

Endocrinol Metab 2007 ; 292 : E253 – 61 . 

218. Voderholzer U , Hornyak M , Thiel B , Huwig-Poppe C , Kiemen A , 

König A , et al. Impact of experimentally induced serotonin 

deficiency by tryptophan depletion on sleep EEG in healthy 

subjects . Neuropsychopharmacology 1998 ; 18 : 112 – 24 . 

219. Waterhouse J , Reilly T , Atkinson G . Jet-lag . Lancet 1997 ; 350 :1611 –6 . 

220. Waterhouse J , Reilly T , Atkinson G , Edwards B . Jet lag: trends 

and coping strategies . Lancet 2007 ; 369 : 1117 – 29 . 

221. Webb WB . The proximal effects of two and four hour naps within 

extended performance without sleep . Psychophysiology 

1987 ; 24 : 426 – 9 . 



222. Wehr TA , Moul DE , Barbato G , Giesen HA , Seidel JA , Barker C , 

et al. Conservation of photoperiod-responsive mechanisms 

in humans . Am J Physiol 1993 ; 265 : R846 – 57 . 

223. Weiss B , Laties VG . Enhancement of human performance by 

caffeine and the amphetamines . Pharmacol Rev 1962 ; 14 : 

1 – 36 . 

224. Wells AS , Read NW , Uvnas-Moberg K , Alster P . Influences of 

fat and carbohydrate on postprandial sleepiness, mood, and 

hormones . Physiol Behav 1997 ; 61 : 679 – 86 . 

225. Wesensten N , Balkin T , Thorne D , Killgore R , Reichardt RM , 

Belenky G . Caffeine, dextroamphetamine modafinil 

during 85 hours of sleep deprivation. I. Performance and 

alertness effects . Aviat Space Environ Med 2004 ; 75 (4, 

Suppl ): B108 . 

226. Wesensten NJ , Belenky G , Kautz MA , Thorne D , Reichardt RM , 

Balkin T . Maintaining alertness and performance during sleep 

deprivation: modafinil versus caffeine . Psychopharmacology 

(Berl) 2002 ; 159 : 238 – 47 . 

227. Wesnes K , Warburton DM . A comparison of temazepam and 

flurazepam in terms of sleep quality and residual changes in 

performance . Neuropsychobiology 1984 ; 11 : 255 – 9 . 

228. Wierwille WW , Ellsworth LA . Evaluation of driver drowsiness 

by trained raters . Accid Anal Prev 1994 ; 26 : 571 

229. Wierwille WW , Wreggit SS , Kim CL , Ellsworth LA , Fairbanks 

RJ . Research on vehicle-based driver status/performance 

monitoring: development, validation, and refinement of 

algorithms for detection of driver drowsiness . Washington, 

DC : National Highway Traffic Safety Administration ; 1994 ; 

Report No: DOT HS 808 247 . 

230. Wing YK . Herbal treatment of insomnia . Hong Kong Med J 2001 ; 

7 : 392 – 402 . 

231. Wirz-Justice A , Armstrong SM . Melatonin. nature’s soporific 

J Sleep Res 1996 ; 5 : 137 – 41 . 

232. Wright N , McGown A . Vigilance on the civil flight deck: 

incidence of sleepiness and sleep during long-haul flights and 

associated changes in physiological parameters . Ergonomics 

2001 ; 44 : 82 – 106 . 

233. Wright N , Powell D , McGown A , Broadbent E , Loft P . Avoiding 

involuntary sleep during civil air operations: Validation of a 

wrist-worn alertness device . Aviat Space Environ Med 2005 ; 

76 : 847 – 56 . 

234. Yesavage JA , Leirer VO . Hangover effects on aircraft pilots 14 h 

after alcohol ingestion: a preliminary report . Am J Psychiatry 

1986 ; 143 : 1546 – 50 . 

235. Youngstedt SD , O’Connor PJ , Dishman RK . Effects of acute exercise 

on sleep: a quantitative synthesis . Sleep 1997 ; 20 :203 –14 . 

236. Zammit GK , Kolevzon A , Fauci M , Shindledecker R , Ackerman 

S . Postprandial sleep in healthy men . Sleep 1995 ; 18 : 229 – 31 . 

237. Zhdanova IV . Melatonin as a hypnotic: pro . Sleep Med Rev 2005 ; 

9 : 51 – 65 .

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